Sulfate compound, non-aqueous electrolyte containing the same, and electrical storage device

Abstract

The present invention relates to a compound represented by formula (I), a non-aqueous electrolyte additive containing the same, a non-aqueous electrolyte, and an electric storage device, and uses thereof as a non-aqueous electrolyte additive.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a sulfate compound, a non-aqueous electrolyte containing the same, and an electricity storage device. Background Art

[0002] In non-aqueous electrolyte secondary batteries, the electrolyte contains a lithium salt, a non-aqueous solvent, and an additive, and a small amount of the additive can specifically solve technical problems such as short cycle life and safety hazards commonly existing in current lithium ion batteries.

[0003] Currently, in non-aqueous electrolyte secondary batteries, VC (vinyl carbonate) is considered the best film-forming additive. Its reduction potential is higher than that of EC (ethylene carbonate), PC (1,3-propane sultone), and DEC (diethyl carbonate), etc., and it can be preferentially reduced on the carbon negative electrode. However, VC is difficult to produce, has a high price, and its high-temperature performance needs to be improved. Therefore, it is necessary to develop an electrolyte additive with better performance, which can improve the film formation of the negative electrode, improve the high-temperature performance of the battery, and improve the cycle stability of the battery.

[0004] CN101847750A discloses a flame-retardant electrolyte for rechargeable lithium batteries, including a lithium salt, a linear carbonate solvent, at least one ammonium cation, a phosphoric acid solvent, and an additive containing oxalate borate, having improved thermal stability, flame retardancy, and electrochemical characteristics such as high rate and cycle life performance. CN107293784A discloses an electrolyte and a lithium ion battery, including a lithium salt, an organic solvent, and an additive, wherein the additive includes a silane phosphate compound and / or a silane borate compound, a fluorocarbon surfactant, and an overcharge prevention additive, and the lithium ion battery has high-temperature storage performance, high-temperature cycle performance, overcharge performance, and rate performance. CN105830271A discloses a phosphonyl formic acid compound, a non-aqueous electrolyte containing the compound, and an electricity storage device, and the non-aqueous electrolyte has the characteristics of maintaining high-load charge and discharge cycles at high temperatures, suppressing the reduction of the thermal stability of the negative electrode, and improving the safety of the electricity storage device. CN103493277A discloses a trifluoromethylbenzene compound, a non-aqueous electrolyte containing the compound, and an electricity storage device, and the non-aqueous electrolyte can improve the electrochemical characteristics within a temperature range. Summary of the Invention

[0005] In one aspect, the present invention provides a compound represented by formula (I)

[0006]

[0007] M is a counter cation;

[0008] m is an integer from 1 to 3;

[0009] X1, X2, X3 and X4 are each independently selected from oxygen and sulfur;

[0010] R1 is selected from halogen, halo-C 1-10 alkyl and halo-C 3-10 cycloalkyl;

[0011] R2 and R3 are each independently selected from halogen, halo-C 1-10 alkyl and halo-C 3-10 cycloalkyl; or

[0012] R2 and R3 are each independently selected from oxygen or sulfur, and R2 and R3 together with the atoms to which they are attached jointly form a moiety represented by formula (II),

[0013]

[0014] wherein X5 and X6 are each independently selected from oxygen or sulfur.

[0015] In a preferred embodiment, X1, X2, X3 and X4 are oxygen.

[0016] In one embodiment, the counter cation is a metal cation or a quaternary amine group.

[0017] In a preferred embodiment, the compound is selected from and combinations thereof, wherein M and m are as defined above;

[0018] In particular, M m+ is a metal cation or a quaternary amine group of

[0019] and m is an integer from 1 to 3.

[0020] In a more preferred embodiment, the compound is selected from

[0021]

[0022] and combinations thereof.

[0023] On the other hand, the present invention provides an additive for non-aqueous electrolyte, which comprises the compound represented by formula (I) of the present invention.

[0024] On yet another hand, the present invention provides a non-aqueous electrolyte, which comprises the compound represented by formula (I) of the present invention and an additive for non-aqueous electrolyte containing the same.

[0025] On the other hand, the present invention provides an electrical energy storage device, which comprises the compound represented by formula (I) of the present invention or the non-aqueous electrolyte of the present invention.

[0026] In still another aspect, the present invention provides the use of the compound represented by formula (I) as an additive for non-aqueous electrolytes.

[0027] In another aspect, the present invention provides an electric device comprising the power storage device of the present invention. Detailed Description

[0028] The present invention will be further described in detail below. Such a description is for illustrative purposes and not intended to limit the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Those skilled in the art can make various modifications and changes without departing from the spirit of the present invention.

[0029] General Definitions and Terms

[0030] All publications, patent applications, patents, and other references mentioned herein are incorporated herein by reference in their entirety if not otherwise indicated.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. In case of contradiction, the definitions provided herein shall prevail.

[0032] Unless otherwise specified, all percentages, parts, ratios, etc. are by weight.

[0033] When a quantity, concentration, or other value or parameter is expressed in the form of a range, a preferred range, or a preferred upper limit of a value and a preferred lower limit of a value, it should be understood that it is equivalent to specifically disclosing any range obtained by combining any pair of upper limits of the range or preferred values with any lower limits of the range or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise indicated, the numerical ranges listed herein are intended to include the endpoints of the range and all integers and fractions within the range. The scope of the present invention is not limited to the specific numerical values cited when defining the range. For example, "1-8" encompasses 1, 2, 3, 4, 5, 6, 7, 8, and any sub-range composed of any two of these values, such as 2-6, 3-5. Again, for example, C 1-10 Alkyl represents an alkyl group having 1-10 carbon atoms, encompassing 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and any sub-range composed of any two of these values, such as 1-8, 2-7, 3-6. Again, for example, C 3-10 Cycloalkyl represents an alkyl group having 3-10 carbon atoms, encompassing 3, 4, 5, 6, 7, 8, 9, 10, and any sub-range composed of any two of these values, such as 3-8, 4-7, 5-6.

[0034] Unless otherwise specified, percentages, parts, ratios, etc. in this text are by weight.

[0035] The terms "about" or "approximately", when used in conjunction with a numerical variable, generally refer to the value of the variable and all values of the variable within the experimental error (e.g., within a 95% confidence interval for the mean value) or within ±10% of the specified value, or within a wider range.

[0036] The terms "comprising", "including", "having", "containing", or "involving" and other variant forms thereof in this text are inclusive or open-ended and do not exclude other unenumerated elements or method steps. Those skilled in the art should understand that the above terms such as "comprising" cover the meaning of "consisting of". The expression "consisting of" excludes any element, step, or component not specified. The expression "consisting essentially of" means that the scope is limited to the specified elements, steps, or components, plus optionally existing elements, steps, or components that do not substantially affect the basic and novel features of the claimed subject matter. It should be understood that the expression "including" covers the expressions "consisting essentially of" and "consisting of".

[0037] The term "selected from..." means one or more elements independently selected from the group listed hereinafter and may include combinations of two or more elements.

[0038] The term "optionally" or "optionally" as used in this text means that the subsequent described event or situation may or may not occur, and this description includes the occurrence and non-occurrence of the described event or situation.

[0039] When describing numerical values or range endpoints in this text, it should be understood that the disclosed content includes the specific values or endpoints cited.

[0040] The term "one or more" or "at least one" as used in this text means one, two, three, four, five, six, seven, eight, nine, or more.

[0041] Unless otherwise specified, the terms "combinations thereof" and "mixtures thereof" represent multi-component mixtures of the respective elements, such as two, three, four, and up to the maximum possible multi-component mixtures.

[0042] The term "halo" or "halogen" or "halo-substituted" should be understood to mean a fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) atom, preferably a fluorine, chlorine, or bromine atom.

[0043] The term "alkyl" refers to a straight-chain or branched-chain saturated aliphatic hydrocarbon group composed of carbon and hydrogen atoms, which is connected to the rest of the molecule by a single bond. "Alkyl" can have 1 - 10 carbon atoms, i.e., "C1 - C 10"Alkyl", such as C1-C4 alkyl, C1-C3 alkyl, C1-C2 alkyl, C3 alkyl, C4 alkyl, C3-C6 alkyl. Non-limiting examples of alkyl include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl, or their isomers. "Subunit" refers to a group obtained by removing one hydrogen atom from a carbon atom with free valence electrons and having two connection sites for connecting to other parts of the molecule. For example, "alkylene" or "alkylidene" refers to a saturated straight-chain or branched-chain divalent hydrocarbon group. Examples of "alkylene" include, but are not limited to, methylene (-CH2-), ethylene (-C2H4-), propylene (-C3H6-), butylene (-C4H8-), pentylene (-C5H 10 -), hexylene (-C6H 12 -), 1-methylethylene (-CH(CH3)CH2-), 2-methylethylene (-CH2CH(CH3)-), methylpropylene or ethylpropylene, etc.

[0044] The term "cycloalkyl", when used alone or in combination with other groups herein, refers to a saturated non-aromatic monocyclic or polycyclic (such as bicyclic) hydrocarbon ring (e.g., monocyclic, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl; or bicyclic, including spiro, fused or bridged systems (such as bicyclo[1.1.1]pentyl, bicyclo[2.2.1]heptyl, bicyclo[3.2.1]octyl or bicyclo[5.2.0]nonyl, decahydronaphthyl, etc.). For example, the term "C 3-10 cycloalkyl" refers to a cycloalkyl having 3-10 ring carbon atoms (such as 3, 4, 5, 6, 7, 8, 9 or 10).

[0045] The compounds of the present invention can be in the form of anions and form salts of the compounds of the present invention with cations. The cations include, but are not limited to, metal cations, ammonium ions, quaternary amine groups.

[0046] The term "counterion" refers to a substance with a charge opposite to that of the compound of the present application, which can be a charged ion, such as a metal cation or an ammonium ion, or a charged group, such as a quaternary amine group.

[0047] The term "linear ester" refers to ester compounds with a linear structure, and examples thereof include, but are not limited to, methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, ethyl methyl carbonate, methyl propyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl propyl carbonate, dipropyl carbonate, etc.

[0048] The term "cyclic ester" refers to ester compounds with a cyclic structure, and examples thereof include, but are not limited to, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one, trans- or cis-4,5-difluoro-1,3-dioxolan-2-one, fluoroethylene carbonate, vinylene carbonate, ethylene vinylene carbonate, propylene carbonate, ethylene carbonate, butylene carbonate.

[0049] The term "electrolyte" is the medium used in chemical batteries, electrolytic capacitors, etc., which can provide ions for the normal operation of chemical batteries, electrolytic capacitors, etc.

[0050] The term "non-aqueous electrolyte" refers to an electrolyte using a non-aqueous solvent.

[0051] The term "electrolyte salt" refers to an ionic salt that is at least partially soluble in the solvent of the electrolyte composition and at least partially dissociates into ions in the solvent of the electrolyte composition to form a conductive electrolyte composition. It is preferred to use lithium salts as electrolyte salts.

[0052] The term "anode" refers to the electrode of an electrochemical cell where oxidation occurs. In a primary battery, such as a battery, the anode is the negatively charged electrode. In a secondary battery (i.e., a rechargeable battery), the anode is the electrode where oxidation occurs during discharge and reduction occurs during charging.

[0053] The term "cathode" refers to the electrode of an electrochemical cell where reduction occurs. In a primary battery, such as a battery, the cathode is the positively charged electrode. In a secondary battery (i.e., a rechargeable battery), the cathode is the electrode where reduction occurs during discharge and oxidation occurs during charging.

[0054] 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 charging.

[0055] The term "secondary battery" refers to an electrochemical cell in which the electrochemical reaction is reversible, and also refers to a battery that can be recharged or is rechargeable for use during its service life by repeated charging and discharging.

[0056] The term "formation" refers to the process of performing small - current charge - discharge on a battery after obtaining it during the battery preparation process. The formation treatment is beneficial to stabilizing the electrical performance of the battery.

[0057] The term "aging" refers to the operation of standing a battery at a certain temperature for a period of time after the battery assembly and liquid injection are completed and the first formation treatment is undergone during the battery preparation process. The aging treatment of the battery helps the SEI structure to reorganize, forming a loose and porous film, making the performance of the battery more stable.

[0058] The term "SEI" or "SEI film" refers to a passivation layer formed on the surface of the electrode material by the reaction of the electrode material and the electrolyte at the solid - liquid phase interface during the first charge - discharge process of the battery.

[0059] The term "electric vehicle" refers to a vehicle powered by electricity. Examples of electric vehicles include, but are not limited to, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug - in hybrid electric vehicles (PHEVs), etc.

[0060] The term "electric two - wheeler" refers to a two - wheeler powered by electricity. Examples of electric two - wheelers include, but are not limited to, E - bicycles and E - scooters.

[0061] Compound of Formula (I)

[0062] In one aspect, the present invention provides a compound of formula (I):

[0063]

[0064] wherein M is a counter - cation; m is an integer from 1 to 3; X1, X2, X3, and X4 are each independently selected from oxygen and sulfur; R1 is selected from halogen, halo - C 1-10 alkyl and halo - C 3-10 cycloalkyl; R2 and R3 are each independently selected from halogen, halo - C 1-10 alkyl and halo - C 3-10 cycloalkyl; or R2 and R3 are each independently selected from oxygen or sulfur, and R2 and R3 together with the atoms to which they are attached jointly form a moiety represented by formula (II),

[0065]

[0066] wherein X5 and X6 are each independently selected from oxygen or sulfur.

[0067] In a preferred embodiment, X1, X2, X3, and X4 are oxygen.

[0068] In a preferred embodiment, R1 is selected from halogens. In a more preferred embodiment, R1 is selected from fluorine, chlorine and bromine. In a particularly preferred embodiment, R1 is fluorine.

[0069] In another embodiment, R2 and R3 are each independently selected from halogens. In a more preferred embodiment, R2 and R3 are each independently selected from fluorine, chlorine and bromine. In a particularly preferred embodiment, R2 and R3 are each independently fluorine.

[0070] In yet another preferred embodiment, R2 and R3 are each independently oxygen, and R2 and R3 together with the atoms attached to them, jointly form the moiety shown in formula (II). In a more preferred embodiment, R2 and R3 are each independently oxygen, and R2 and R3 together with the atoms attached to them, jointly form the moiety shown in formula (II), wherein X5 and X6 are each independently oxygen.

[0071] In a specific embodiment, R1 is fluorine and R2 and R3 are each independently fluorine. In another specific embodiment, R1 is fluorine, R2 and R3 are each independently oxygen, and R2 and R3 together with the atoms attached to them, jointly form the moiety shown in formula (II), wherein X5 and X6 are each independently oxygen.

[0072] According to the valence state of the counter cation M m+ , m corresponds to an integer from 1 to 3. For example, when the counter cation M m+ is a lithium ion (Li + ), m corresponds to 1 and R is a substituent as defined above. Another example is when the counter cation M m+ is a calcium ion (Ca 2+ ), m corresponds to 2. Another example is when the counter cation M m+ is a quaternary amine group, m corresponds to 1.

[0073] In a preferred embodiment, the compound is selected from

[0074] and combinations thereof, wherein M and m are as defined above;

[0075] In particular, M m+ is a metal cation or a quaternary amine group as described above, and m is an integer from 1 to 3.

[0076] In a more preferred embodiment, the compound is selected from

[0077] (also represented herein as LiSF3C2O5),

[0078] (also represented as LiSFC4O9 in this text),

[0079] (also represented as TBASF3C2O5 in this text),

[0080] (also represented as TBASFC4O9 in this text) and combinations thereof.

[0081] In this text, TBA + is represented as the quaternary ammonium group tetrabutylammonium, i.e., Therefore can also be represented as

[0082] Counter Cation

[0083] The counter cations in the compounds of this text include but are not limited to metal cations, ammonium ions, quaternary ammonium groups, etc.

[0084] In a preferred embodiment, the counter cation is a metal cation or a quaternary ammonium group.

[0085] In a more preferred embodiment, the counter cation is a metal cation. Metal cations can include alkali metal cations, alkaline earth metal cations, transition metal cations, etc. In a preferred embodiment, the metal cation contained in the compound of formula (I) is an alkali metal cation or an alkaline earth metal cation. In a more preferred embodiment, the metal cation contained in the compound of formula (I) is selected from lithium ions, sodium ions, potassium ions, calcium ions, magnesium ions and combinations thereof. In a particularly preferred embodiment, the metal cation contained in the compound of formula (I) is a lithium ion.

[0086] In another more preferred embodiment, the counter cation is a quaternary ammonium group. In a preferred embodiment, the quaternary ammonium group contained in the compound of formula (I) is selected from tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium. In a more preferred embodiment, the quaternary ammonium group contained in the compound of formula (I) is tetrabutylammonium.

[0087] Additive for Non-Aqueous Electrolyte

[0088] On the other hand, the present invention provides an additive for non-aqueous electrolytes, characterized in that it contains the compound represented by the above formula (I).

[0089] Non-Aqueous Electrolyte Containing Compound of Formula (I)

[0090] On the other hand, the present invention provides a non-aqueous electrolyte comprising the compound represented by formula (I) of the present invention. In the non-aqueous electrolyte of the present invention, one or more compounds represented by formula (I) of the present invention may be included, that is, a compound represented by one formula (I) may be used, or a mixture or combination of more than one compound represented by formula (I) may be used.

[0091] As an additive in the non-aqueous electrolyte, the compound represented by formula (I) can be reduced and form a film on the negative electrode, passivate the electrode surface, allow lithium ions to freely enter and exit the electrode while solvent molecules cannot penetrate, thereby preventing the damage to the electrode caused by the co-insertion of solvent molecules, and improving the performance such as the cycle efficiency and reversible capacity of the battery containing the non-aqueous electrolyte. In addition, the compound of formula (I) has a relatively high reduction voltage, can be preferentially reduced and form a film on the negative electrode, improve the high-temperature performance of the battery containing the non-aqueous electrolyte, and improve the cycle stability of the battery.

[0092] In one embodiment, based on the total weight of the non-aqueous electrolyte, the content of the compound of formula (I) in the non-aqueous electrolyte is about 0.1 - 10% by weight. In a preferred embodiment, based on the total weight of the non-aqueous electrolyte, the content of the compound of formula (I) in the non-aqueous electrolyte is about 0.2 - 6% by weight. In a more preferred embodiment, based on the total weight of the non-aqueous electrolyte, the content of the compound of formula (I) in the non-aqueous electrolyte is about 1% by weight. For example, about 0.1% by weight, about 0.2% by weight, about 0.3% by weight, about 0.5% by weight, about 0.8% by weight, about 1% by weight, about 1.5% by weight, about 2% by weight, about 3% by weight, about 4% by weight, about 5% by weight, about 6% by weight, about 7% by weight, about 8% by weight, about 8.5% by weight, about 9% by weight, about 10% by weight. Too low content of the compound of formula (I) cannot effectively improve the cycle life of the battery containing the non-aqueous electrolyte. While too high content of the compound of formula (I) will cause the battery containing the non-aqueous electrolyte to generate excessive gas during high-temperature operation, leading to the problem of battery swelling.

[0093] Non-Aqueous Solvent

[0094] In one embodiment, the non-aqueous electrolyte may contain a non-aqueous solvent. Examples of non-aqueous solvents that can be used include, but are not limited to, cyclic esters, chain esters, ethers, amides, phosphate esters, sulfones, nitriles, compounds containing S=O bonds, etc.

[0095] In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvent used is selected from cyclic esters, chain esters and combinations thereof.

[0096] Cyclic carbonate

[0097] Cyclic esters include, but are not limited to, cyclic carbonates and lactones. In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvent used is a cyclic carbonate.

[0098] Examples of cyclic carbonates include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,2-butylene carbonate, 2,3-butylene carbonate, vinylene carbonate, ethylene vinyl carbonate (VEC), trans- or cis-4,5-difluoro-1,3-dioxolan-2-one (collectively referred to as "DFEC"), 4-ethynyl-1,3-dioxolan-2-one (EEC), propylene carbonate, ethylene carbonate, butylene carbonate, etc.

[0099] In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvent used is selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, propylene carbonate and combinations thereof. In a more preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvent used is ethylene carbonate.

[0100] In another preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvent used is a cyclic carbonate containing unsaturated bonds such as carbon-carbon double bonds or carbon-carbon triple bonds. In a more preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvent used is selected from vinylene carbonate, ethylene vinyl carbonate, 4-ethynyl-1,3-dioxolan-2-one and combinations thereof. In a particularly preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvent used is vinylene carbonate.

[0101] In yet another preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous electrolyte used is a cyclic carbonate containing fluorine atoms. In a more preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous electrolyte used is selected from fluoroethylene carbonate, trans- or cis-4,5-difluoro-1,3-dioxolan-2-one and combinations thereof.

[0102] The content of a suitable cyclic carbonate non-aqueous solvent containing unsaturated bonds helps to improve the low-temperature and high-temperature characteristics of the battery containing the non-aqueous electrolyte and improve the load characteristics after high-temperature charge storage. An excessive content of the cyclic carbonate containing unsaturated bonds will increase the viscosity of the electrolyte, reduce the charge transfer efficiency in the battery, and reduce the efficiency of the battery. An insufficient content of the cyclic carbonate containing unsaturated bonds will reduce the conductivity of the battery and reduce the efficiency of the battery.

[0103] The content of a suitable non-aqueous solvent of a cyclic carbonate containing fluorine atoms helps to improve the low-temperature and high-temperature characteristics of a battery comprising the non-aqueous electrolyte, and also improves the load characteristics after high-temperature charge storage. An excessively high content of the cyclic carbonate containing fluorine atoms will increase the viscosity of the electrolyte, reduce the charge transfer efficiency in the battery, and lower the battery efficiency. An excessively low content of the cyclic carbonate containing fluorine atoms will reduce the conductivity of the battery and lower the battery efficiency.

[0104] In some embodiments, the non-aqueous solvent is a single cyclic carbonate solvent.

[0105] In other embodiments, the non-aqueous solvent is a mixed solvent. In a preferred embodiment, the non-aqueous solvent comprises two or more cyclic carbonate solvents. When using a mixed solvent, the electrochemical performance of a battery comprising the non-aqueous electrolyte at high temperatures can be further improved. In another preferred embodiment, the non-aqueous solvent comprises three or more cyclic carbonate solvents. The combinations of mixed cyclic carbonates include but are not limited to cyclic carbonate and cyclic carbonate containing an unsaturated bond, cyclic carbonate and cyclic carbonate containing a fluorine atom, cyclic carbonate containing an unsaturated bond and cyclic carbonate containing a fluorine atom, or cyclic carbonate and cyclic carbonate containing an unsaturated bond and cyclic carbonate containing a fluorine atom, etc., where the selection of cyclic carbonate, cyclic carbonate containing an unsaturated bond, and cyclic carbonate containing a fluorine atom is as described above.

[0106] Chain carbonate

[0107] Chain esters include but are not limited to chain carbonates and chain sulfonates. In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvent used is a chain carbonate.

[0108] Examples of chain carbonates include but are not limited to ethyl methyl carbonate (EMC), methyl propyl carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl propyl carbonate, dipropyl carbonate, etc.

[0109] In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous electrolyte used is preferably selected from ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl propyl carbonate, dipropyl carbonate, and combinations thereof. In a more preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous electrolyte used is preferably selected from ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and combinations thereof.

[0110] For a battery comprising the non-aqueous electrolyte, a suitable content of chain carbonate helps to obtain good battery performance. An excessively high content of chain carbonate will reduce the conductivity of the battery and lower the battery efficiency. An excessively low content of chain carbonate will increase the viscosity of the electrolyte, reduce the charge transfer efficiency in the battery, and lower the battery efficiency.

[0111] In some embodiments, the non-aqueous solvent is a single-chain carbonate solvent.

[0112] In other embodiments, the non-aqueous solvent is a mixed solvent. In a preferred embodiment, the non-aqueous solvent comprises more than 2 chain carbonate solvents. When using a mixed solvent, the electrochemical performance of a battery comprising the non-aqueous electrolyte at high temperatures can be further improved. In another preferred embodiment, the non-aqueous solvent comprises more than 3 chain carbonate solvents. When the non-aqueous solvent of the non-aqueous solvent electrolyte is a mixture of chain carbonates, its selection is as described above.

[0113] Other solvents

[0114] Lactones

[0115] In one embodiment, the lactone as the non-aqueous solvent is selected from γ-butyrolactone, γ-valerolactone, α-angelica lactone, and combinations thereof.

[0116] Ethers

[0117] In one embodiment, the ether as the non-aqueous solvent is selected from cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 1,3-dioxane, and 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, and combinations thereof.

[0118] Amides

[0119] In one embodiment, the amide as the non-aqueous solvent is dimethylformamide.

[0120] Phosphate esters

[0121] In one embodiment, the phosphate ester as the non-aqueous solvent is selected from trimethyl phosphate, tributyl phosphate, trioctyl phosphate, and combinations thereof.

[0122] Nitriles

[0123] In one embodiment, the nitrile as the non-aqueous solvent is selected from acetonitrile, propionitrile, succinonitrile, glutaronitrile or adiponitrile, pimelonitrile, and combinations thereof.

[0124] Compounds containing S=O bonds

[0125] In one embodiment, the S═O bond-containing compound as the non-aqueous solvent is selected from sultone compounds such as 1,3-propane sultone, 1,3-butane sultone, and 1,4-butane sultone; cyclic sulfite compounds such as ethylene sulfite, hexahydrobenzo[1,3,2]dioxathiolane-2-oxide (also referred to as 1,2-cyclohexanediol cyclic sulfite), and 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide; sulfonate compounds such as 1,2-ethylene dimethanesulfonate, 1,2-propylene dimethanesulfonate, 1,3-propylene dimethanesulfonate, 1,4-butylene dimethanesulfonate, 1,5-pentylene dimethanesulfonate, 2-propynyl methanesulfonate, and methylene methanedisulfonate; divinyl sulfone, 1,2-bis(vinylsulfonyl)ethane, bis(2-vinylsulfonylethyl), and combinations thereof.

[0126] To achieve appropriate physical properties, the above non-aqueous solvents can be used in combination. The non-aqueous solvents used in combination are selected from cyclic carbonates, chain carbonates, ethers, amides, phosphate esters, sulfones, nitriles, and S═O bond-containing compounds, and the selection of cyclic carbonates, chain carbonates, ethers, amides, phosphate esters, sulfones, nitriles, and S═O bond-containing compounds is as described above.

[0127] In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvents used are a combination of a cyclic carbonate and a chain carbonate, and the selection of the cyclic carbonate and the chain carbonate is as described above. For a battery containing such a non-aqueous electrolyte, such a combination can improve the low-temperature and high-temperature cycle characteristics and the load characteristics after high-temperature charge storage.

[0128] For a battery containing such a non-aqueous electrolyte, an appropriate mass ratio of the cyclic carbonate to the chain carbonate helps to obtain good battery performance. In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the mass ratio of the cyclic carbonate solvent to the chain carbonate solvent is 3:7. An excessively high mass ratio of the cyclic carbonate solvent to the chain carbonate solvent will increase the viscosity of the electrolyte, reduce the charge transfer efficiency in the battery containing such a non-aqueous electrolyte, and reduce the battery efficiency. An excessively low mass ratio of the cyclic carbonate solvent to the chain carbonate solvent will reduce the conductivity of the battery and reduce the battery efficiency.

[0129] In a specific embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvents used are ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvents used are ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate, and their mass ratio is 3:4:3 - 3:6:1. In a more preferred embodiment, in the non-aqueous electrolyte of the present invention, the non-aqueous solvents used are ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate, and their mass ratio is 3:5:2.

[0130] Electrolyte Salt

[0131] An electrolyte salt refers to an ionic salt that is at least partially soluble in the solvent of the electrolyte composition and at least partially dissociates into ions in the solvent of the electrolyte composition to form a conductive electrolyte composition.

[0132] In one embodiment, in the non-aqueous electrolyte of the present invention, a lithium salt or an onium salt is used as the electrolyte salt. In a more preferred embodiment, in the non-aqueous electrolyte of the present invention, a lithium salt is used as the electrolyte salt.

[0133] Lithium salt

[0134] A lithium salt refers to a salt having lithium as a cation. During the operation of the battery, the lithium ions of the electrolyte lithium salt play a role in transporting ions between the positive and negative electrodes of the battery, which is crucial for the performance of the battery. In addition, the type, purity, content of the electrolyte lithium salt in the battery, and the combination of the lithium salt with other substances can affect the capacity, charge and discharge performance, lifespan, and safety of the battery to varying degrees.

[0135] In the non-aqueous electrolyte of the present invention, the lithium salts used include a first lithium salt and a second lithium salt, where the first lithium salt is an inorganic lithium salt and the second lithium salt is a lithium salt containing an organic group.

[0136] First lithium salt

[0137] In one embodiment, in the non-aqueous electrolyte of the present invention, the first lithium salt used is selected from LiPF6, LiBF4, LiBCl4, LiAsF6, LiClO4, LiAlO2, LiCl, LiI, LiSbF6, and combinations thereof. In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the first lithium salt used is selected from LiPF6, LiBF4, and combinations thereof.

[0138] The first lithium salt generally has good ionization ability and is easily ionized in the solvent, thus obtaining a large number of free lithium ions. Therefore, a suitable first lithium salt helps to provide a sufficient content of lithium ions for the non-aqueous electrolyte and improve the conductivity of the non-aqueous electrolyte. In one embodiment, the content of the first lithium salt is about 8-16% by weight. In a preferred embodiment, the content of the first lithium salt is about 10-15% by weight. In a more preferred embodiment, the content of the first lithium salt is about 13.5-14.5% by weight. For example, about 8% by weight, about 8.5% by weight, about 9% by weight, about 9.5% by weight, about 10% by weight, about 10.5% by weight, about 11% by weight, about 11.5% by weight, about 12% by weight, about 12.5% by weight, about 13% by weight, about 13.5% by weight, about 13.9% by weight, about 14% by weight, 14.1% by weight, about 14.5% by weight, about 15% by weight, about 15.5% by weight, about 16% by weight. An excessive content of the first lithium salt will increase the viscosity of the non-aqueous electrolyte, reduce the charge transfer efficiency in the battery containing the non-aqueous electrolyte, and thus reduce the battery efficiency.

[0139] The second lithium salt

[0140] In one embodiment, in the non-aqueous electrolyte of the present invention, the second lithium salt used is selected from lithium salts containing a P=O structure, lithium salts containing a -S(=O)2- structure, lithium salts having a boron oxalate complex as an anion, and combinations thereof.

[0141] Lithium salts containing a P=O structure include, but are not limited to, lithium difluorophosphate (LiPO2F2), lithium monofluorophosphate (Li2PO3F), etc.

[0142] Lithium salts containing a -S(=O)2- structure include, but are not limited to, lithium salts containing a -S(=O)2O structure, lithium salts containing a -S(=O)2-N - -S(=O)2- structure lithium salts, etc. In a preferred embodiment, the lithium salt containing a -S(=O)2- structure is a lithium salt containing a -S(=O)2-N - -S(=O)2- structure lithium salt. In a more preferred embodiment, the lithium salt containing a -S(=O)2-N - -S(=O)2- structure lithium salt is selected from lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)amide (LiTFSI), etc.

[0143] Lithium salts having a boron oxalate complex as an anion include, but are not limited to, lithium bis(oxalato)difluorophosphate (LiODFP), lithium difluoro(oxalato)borate (LiODFB), lithium borate (LiBOB), etc.

[0144] In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the second lithium salt used is selected from LiPO2F2, Li2PO3F, LiODFB, LiODFP, LiBOB, LiTFSI, LiFSI, and combinations thereof. In a more preferred embodiment, in the non-aqueous electrolyte of the present invention, the second lithium salt used is selected from LiPO2F2, LiODFB, LiODFP, LiBOB, LiTFSI, LiFSI, and combinations thereof.

[0145] The suitable second lithium salt can participate in the formation of the electrode film while providing a small amount of lithium ions, which helps to improve the performance of the battery containing the non-aqueous electrolyte. In one embodiment, the content of the second lithium salt is about 0.5 - 5 wt%. In a preferred embodiment, the content of the second lithium salt is about 1.5 - 4 wt%. In a more preferred embodiment, the content of the second lithium salt is about 1.9 - 3.6 wt%. For example, about 0.5 wt%, about 0.8 wt%, about 1 wt%, about 1.5 wt%, about 1.9 wt%, about 2 wt%, about 2.3 wt%, about 2.5 wt%, about 2.8 wt%, about 3 wt%, about 3.3 wt%, about 3.5 wt%, about 3.6 wt%, about 4 wt%, about 4.5 wt%, about 5 wt%. An excessively high content of the second lithium salt will increase the viscosity of the electrolyte, reduce the charge transfer efficiency in the battery, and lower the battery efficiency. An excessively low content of the second lithium salt will not be able to improve the performance of the battery containing the non-aqueous electrolyte. In one embodiment, in the non-aqueous electrolyte of the present invention, a combination of the first lithium salt and the second lithium salt is used as the electrolyte lithium salt. Such a combination helps to improve the thermal stability of the battery anode and improve the lithium ion permeability.

[0146] The total content of the suitable first lithium salt and second lithium salt helps the lithium salts to interact with other additives, achieving the effects of reducing impedance and suppressing gas generation, and is also conducive to improving the formation of the electrode film. In one embodiment, in the non-aqueous electrolyte of the present invention, the total content of the first lithium salt and the second lithium salt is about 10-20% by weight. In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the total content of the first lithium salt and the second lithium salt is about 11-17.6% by weight. In a more preferred embodiment, in the non-aqueous electrolyte of the present invention, the total content of the first lithium salt and the second lithium salt is about 15.4-17.5% by weight. For example, about 10% by weight, about 11% by weight, about 12% by weight, about 12.5% by weight, about 13% by weight, about 13.5% by weight, about 14% by weight, about 15% by weight, about 15.4% by weight, about 15.5% by weight, about 16% by weight, about 16.3% by weight, about 16.5% by weight, about 17% by weight, about 17.5% by weight, about 17.6% by weight, about 18% by weight, about 19% by weight, about 20% by weight. An excessively high total content of the first lithium salt and the second lithium salt will increase the viscosity of the electrolyte, reduce the charge transfer efficiency in the electrolyte, and reduce the conductivity. An excessively low total content of the first lithium salt and the second lithium salt cannot achieve its function of increasing the conductivity of the electrolyte.

[0147] Other Additives

[0148] In the non-aqueous electrolyte of the present invention, other additives selected from the following may also be optionally included: linear carbonates, cyclic carbonates, cyclic sulfonic esters, or combinations thereof.

[0149] The selection of the linear carbonate and the cyclic carbonate is as described above, where the linear carbonate and the cyclic carbonate are selected from other carbonates except the solvent.

[0150] Examples of the cyclic sulfonic ester include but are not limited to 1,3-propane sultone (PS), vinylene sulfate (DTD), etc.

[0151] In one embodiment, in the non-aqueous electrolyte of the present invention, one or more additives selected from the following are further included: vinylene carbonate, fluoroethylene carbonate, dimethyl carbonate, 1,3-propane sultone, vinylene sulfate, propylene carbonate.

[0152] In one embodiment, in the non-aqueous electrolyte of the present invention, the content of the other additives is about 0-10% by weight. In a preferred embodiment, in the non-aqueous electrolyte of the present invention, the content of the other additives is about 2-7% by weight. In a more preferred embodiment, in the non-aqueous electrolyte of the present invention, the content of the other additives is about 4-6% by weight. Suitable other additive contents, such as about 0% by weight, about 1% by weight, about 2% by weight, about 2.5% by weight, about 3% by weight, about 3.5% by weight, about 4% by weight, about 4.5% by weight, about 5% by weight, about 5.5% by weight, about 6% by weight, about 7% by weight, about 8% by weight, about 9% by weight, about 10% by weight, are beneficial to improving the performance of the battery, such as the high-temperature stability, low-temperature stability, and film-forming stability of the battery. For example, adding vinylene sulfate to the non-aqueous electrolyte of the present invention can effectively improve the low-temperature performance of the battery containing the non-aqueous electrolyte, and is also beneficial to the high-temperature cycle performance and high-temperature storage performance.

[0153] Electrical Energy Storage Device

[0154] In yet another aspect, the present invention provides an electricity storage device comprising the compound represented by formula (I) of the present invention, or the non-aqueous electrolyte of the present invention.

[0155] In a preferred embodiment, the electricity storage device is a secondary battery, which comprises a positive electrode, a negative electrode, and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent. In the present invention, the constituent components such as the positive electrode and the negative electrode other than the non-aqueous electrolyte of the present invention can be used without particular limitation.

[0156] Positive electrode material

[0157] The active material of the positive electrode can be a composite metal oxide composed of lithium and one or more selected from cobalt, manganese, and nickel. In one embodiment, the positive electrode active material is a single component. In another embodiment, the positive electrode active material is a mixture of the above composite metal oxides.

[0158] In a preferred embodiment, the lithium composite metal oxide used in the present invention is selected from LiCoO2, LiMn2O4, LiNiO2, LiCo 1-x Ni x O2 (0.01 < x < 1), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.65 Co 0.15 Mn 0.2 O2, LiNi 0.55 Co 0.15 Mn 0.3 O2, LiNi0.8 Co 0.1 Mn 0.1 O2, LiNi 0.55 Co 0.1 Mn 0.35 O2, LiNi 1 / 2 Mn 3 / 2 O4, LiCo 0.98 Mg 0.02 O2 and their combinations. In a more preferred embodiment, the lithium composite metal oxide used in the present invention is selected from LiNi 0.65 Co 0.15 Mn 0.2 O2, LiNi 0.55 Co 0.15 Mn 0.3 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.55 Co 0.1 Mn 0.35 O2 and their combinations.

[0159] In addition, in order to improve the safety or cycle characteristics during overcharging, or to be able to be used at a charging potential above 4.3 V, a part of the lithium composite metal oxide can also be replaced with other elements. For example, a part of cobalt, manganese, and nickel can be replaced with at least one element such as Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, Cu, Bi, Mo, La, etc., or a part of O can be replaced with S or F, or a compound containing these other elements can be coated.

[0160] Among them, it is preferably a lithium composite metal oxide that can be used when the charging potential of the positive electrode is 4.3 V or more based on Li in the fully charged state, such as LiCoO2, LiMn2O4, LiNiO2. More preferably, it is a lithium composite metal oxide in which the solid solution can be used at 4.4 V or more, such as LiCo 1-x M x O2 (where M is at least one element selected from Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, Cu, 0.001 ≤ x ≤ 0.05), LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.65 Co 0.15 Mn 0.2 O2, LiNi 0.55 Co 0.15 Mn 0.3 O2, LiNi 0.8 Co 0.1Mn 0.1 O2 or LiNi 0.55 Co 0.1 Mn 0.35 O2, LiNi 1 / 2 Mn 3 / 2 O4, Li2MnO3 and LiMO2 (M is a transition metal such as Co, Ni, Mn, Fe, etc.). If a lithium composite metal oxide that operates at a high charging voltage is used, since it reacts with the electrolyte during charging, the electrochemical characteristics of the electrode are likely to deteriorate at particularly high temperatures. However, in the secondary battery of the present invention, these deteriorations in electrochemical characteristics can be suppressed. Particularly in the case of a positive electrode containing Mn, since there is dissolution of Mn ions from the positive electrode, the resistance of the battery tends to increase. Therefore, when used in a wide temperature range, the electrochemical characteristics of the electrode tend to deteriorate. In the secondary battery of the present invention, by using the above materials as the positive electrode material of the battery, these deteriorations in electrochemical characteristics can be suppressed.

[0161] The positive electrode can be prepared by the following exemplary method: Mix the above positive electrode active material with a conductive agent such as acetylene black and carbon black, and a binder such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), a copolymer of acrylonitrile and butadiene (NBR), carboxymethyl cellulose (CMC), and an ethylene - propylene - diene terpolymer. After adding a high - boiling - point solvent such as 1 - methyl - 2 - pyrrolidone and kneading to form a positive electrode mixture, coat the positive electrode mixture onto a current collector such as an aluminum foil or a strip made of stainless steel, dry it, and after pressure molding, perform a heat treatment at a temperature of about 50 - 250°C under vacuum for about 2 hours.

[0162] Negative electrode material

[0163] The active material of the negative electrode can be a carbon material capable of intercalating or deintercalating lithium metal or lithium alloy, including but not limited to easily graphitizable carbon, hardly graphitizable carbon with an interplanar distance of the (002) plane of 0.37 nm or more, and graphite with an interplanar distance of the (002) plane of 0.34 nm or less. In addition, the negative electrode active material can also be tin (elemental), tin compounds, silicon (elemental), silicon compounds, Li4Ti5O 12 and other lithium titanate compounds and their combinations.

[0164] In a preferred embodiment, the negative electrode active material used in the power storage device of the present invention is selected from elemental silicon, silicon compounds, artificial graphite, natural graphite, or silicon - oxygen composite artificial graphite. In a more preferred embodiment, the negative electrode active material used in the power storage device of the present invention is selected from artificial graphite, natural graphite, or silicon - oxygen composite artificial graphite.

[0165] The negative electrode can be prepared by the following method: After kneading the same conductive agent, binder, and high-boiling solvent as those used in the production of the above-mentioned positive electrode to form a negative electrode mixture, the negative electrode mixture is coated on a copper foil or the like of a current collector, dried, and pressure-molded, and then heat-treated under vacuum at a temperature of about 50 - 250 °C for about 2 hours.

[0166] Manufacture of secondary battery

[0167] The secondary battery of the present invention can be prepared by the following exemplary method:

[0168] Stack the positive and negative electrode sheets and a separator made of polyethylene in the order of negative electrode, separator, positive electrode, separator, and end with the negative electrode to obtain a bare battery cell. The bare battery cell is hot-pressed so that polyvinylidene fluoride (PVDF) on the surface of the separator bonds the electrode sheets together. After welding the tabs of the hot-pressed bare battery cell, it is placed in a pre-punched aluminum-plastic film and heat-sealed to obtain a pre-packaged battery with a liquid injection port. The pre-packaged battery is placed in a vacuum furnace for sufficient baking and drying, a certain amount of electrolyte is injected from the liquid injection port, and the liquid injection port is sealed in a vacuum environment to obtain a secondary battery.

[0169] Performance of Secondary Battery

[0170] The secondary battery of the present invention can be tested by the following method.

[0171] (1) Initial discharge capacity test of secondary battery

[0172] Place the prepared battery on a fixture, charge the battery at a first constant current to 4.3 V at 25 °C, and then discharge it at a second constant current to 2.8 V. Optionally, repeat the above operation for a second cycle to stabilize the battery. Optionally, perform a third charge-discharge cycle, in which after charging to 4.3 V at a third constant current, charge at a constant voltage of 4.3 V until the current value reaches 0.05 C current, and discharge at a fifth constant current to 2.8 V. Optionally, perform a fourth charge-discharge cycle, in which after charging to 4.3 V at a sixth constant current, charge at a constant voltage of 4.3 V until the current value reaches 0.05 C, and discharge at a seventh constant current to 2.8 V. After the above operations, the initial discharge capacity can be finally obtained. The first to seventh constant currents can be 1 C, 5 C, 0.1 C, 0.2 C, etc. 1 C represents the current value for discharging the reference capacity of the battery in 1 hour, 5 C represents 5 times the above current value, and 0.1 C and 0.2 C represent 1 / 10 and 1 / 5 of the above current value, respectively.

[0173] (2) Cycle test of secondary battery

[0174] Perform cyclic charge and discharge within the specified potential range at a current of 1C, record the capacity of each cycle, and end the test when the battery capacity reaches 80% of the initial cycle capacity.

[0175] (3) Test of the DC resistance (DCR) of the secondary battery

[0176] At the specified temperature, discharge the battery at a current of 1C until the state of charge (SOC) reaches 50%, then increase the current to 4C and maintain it for 30s. Detect the difference between the updated stable voltage and the original platform voltage. The ratio of this value to the 3C current value is the DC resistance of the battery. Compare the DCR after cycling with the DCR at the start of cycling to obtain the growth rate of DCR.

[0177] (4) Test of the change in the volume of gas generated by the secondary battery

[0178] Fix the secondary battery with a thin string and completely immerse it in water at 25°C. Record the weight difference before and after immersion, and convert it to a volume difference based on the density of water at 25°C.

[0179] (5) Test of the capacity recovery rate of the secondary battery at 60°C

[0180] Place the charged secondary battery in an environment at 60°C and leave it for 60 days. Measure the reversible capacity after 60 days to obtain the capacity recovery rate compared to 60 days ago.

[0181] In one embodiment, the initial DC resistance (DCR) of the secondary battery of the present invention is about 1.10 - 1.35 mohm. In a preferred embodiment, the initial DC resistance (DCR) of the secondary battery of the present invention is preferably about 1.12 - 1.35 mohm. For example, about 1.10 mohm, about 1.12 mohm, about 1.13 mohm, about 1.14 mohm, about 1.15 mohm, about 1.17 mohm, about 1.2 mohm, about 1.21 mohm, about 1.22 mohm, about 1.23 mohm, about 1.24 mohm, about 1.25 mohm, about 1.26 mohm, about 1.27 mohm, about 1.28 mohm, about 1.29 mohm, about 1.30 mohm, about 1.31 mohm, about 1.32 mohm, about 1.33 mohm, about 1.34 mohm, about 1.35 mohm, about 1.36 mohm, about 1.37 mohm, about 1.38 mohm, about 1.39 mohm, about 1.40 mohm.

[0182] In one embodiment, after the above four charge-discharge cycles, the growth rate of the DC resistance of the secondary battery of the present invention is about 15% - about 35%. In a preferred embodiment, after the above four charge-discharge cycles, the growth rate of the DC resistance of the secondary battery of the present invention is about 20% - about 29%. For example, about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%, about 32%.

[0183] In one embodiment, after the above four charge-discharge cycles, the growth rate of the gas volume generated by the secondary battery of the present invention is about 3% - about 20%. In a preferred embodiment, after the above four charge-discharge cycles, the growth rate of the gas volume generated by the secondary battery of the present invention is about 3% - about 11%. For example, it is about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%.

[0184] In one embodiment, after the secondary battery of the present invention is placed in an environment of 60 °C for 60 days, the growth rate of the DC resistance of the secondary battery is about 10% - about 30%. In a preferred embodiment, after the secondary battery of the present invention is placed in an environment of 60 °C for 60 days, the growth rate of the DC resistance of the secondary battery is about 15% - about 22%. For example, about 5%, about 10%, about 15%, about 20%, about 21%, about 22%, about 23%, about 25%, about 30%.

[0185] In one embodiment, after the secondary battery of the present invention is placed in an environment of 60 °C for 60 days, the capacity recovery rate of the secondary battery is about 90% - about 98%. In a preferred embodiment, after the secondary battery of the present invention is placed in an environment of 60 °C for 60 days, the capacity recovery rate of the secondary battery is about 92% - about 98%. For example, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%.

[0186] In one embodiment, after the secondary battery of the present invention is placed in an environment of 60 °C for 60 days, the growth rate of the gas volume generated by the secondary battery is about 1% - about 50%. In a preferred embodiment, after the secondary battery of the present invention is placed in an environment of 60 °C for 60 days, the growth rate of the gas volume generated by the secondary battery is about 1% - about 10%. For example, about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%.

[0187] In one embodiment, after the secondary battery of the present invention is placed in an environment of -30 °C and the above four charge-discharge cycles are carried out, the growth rate of the DC resistance of the secondary battery of the present invention is about 10%.

[0188] In one embodiment, when the secondary battery of the present invention reaches 80% SOH, the number of cycles is about 1900 - 2800. In a preferred embodiment, when the secondary battery of the present invention reaches 80% SOH, the number of cycles is about 1995 - 2501. For example, about 1995, about 2004, about 2125, about 2131, about 2198, about 2209, about 2212, about 2293, about 2501.

[0189] Electric Device

[0190] In one aspect, the present invention provides an electric device, characterized in that the electric device comprises the power storage device of the present invention.

[0191] In a preferred embodiment, the electric device is selected from electric vehicles, electric two-wheelers, and power storage systems.

[0192] In a more preferred embodiment, the electric device is an electric vehicle, and the electric vehicle is preferably selected from electric vehicles (EV), hybrid vehicles (HEV), and plug-in hybrid vehicles (PHEV).

[0193] In yet another aspect, the present invention also relates to the use of the compound of formula (I) as an additive for non-aqueous electrolyte.

[0194] Advantageous Effects

[0195] Using the compound of formula (I) as an additive for non-aqueous solvent electrolyte can improve the formation of the negative electrode film of the secondary battery of the present invention, so that the cycle stability of the secondary battery of the present invention can be improved. After the secondary battery undergoes multiple charge and discharge cycles, both the DC resistance and the growth rate of the gas generation volume of the secondary battery are relatively low. In addition, after adding the compound of formula (I) to the non-aqueous solvent electrolyte of the secondary battery, the high-temperature performance of the secondary battery, such as high-temperature stability, etc. can also be improved. Among them, after the secondary battery of the present invention is placed in an environment of 60 °C for 60 days, the growth rates of the DC resistance and the gas generation volume of the secondary battery only change slightly, and the capacity recovery rate is as high as over 92%. In addition, after adding the compound of formula (I) to the non-aqueous solvent electrolyte of the secondary battery, the low-temperature performance of the secondary battery can also be improved.

[0196] Examples

[0197] It should be noted that the following examples are only illustrations for clearly explaining the technical solutions of the present invention, rather than limitations on the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here, and the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

[0198] Unless otherwise specified, the instruments, equipment, reagents and materials used herein are all commercially available.

[0199] Instruments

[0200] Thermostat: purchased from Jufu Instrument Industry Co., Ltd. (EEPCT - 408 - 40 - SSP - AR)

[0201] Charge and discharge machine: purchased from Shenghong (BTS0510C80 - HP)

[0202] Materials

[0203] The reagents used herein, such as ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, LiPF6, etc., are purchased from Shanghai Guoyao or Sigma - Aldrich.

[0204] In Comparative Examples 3 - 5, the compounds LiSC4O8, LiSF2C2O4 or their combinations in the prior art are used as additives for secondary batteries, and the structure of LiSC4O8 is The structure of LiSF2C2O4 is

[0205] The structure of the compound is determined by nuclear magnetic resonance ( 19 19F NMR) and liquid chromatography - mass spectrometry (HPLC - MS).

[0206] 19 19F NMR is measured with a Bruker 500MHz AVANCE III nuclear magnetic resonance instrument. The measurement solvent is deuterated chloroform (CDCl3), the internal standard is deuterated fluoroform (CDF3), and the chemical shift (δ) is given in units of 10 -6 (ppm).

[0207] Ion chromatography is used for liquid chromatography. Chromatographic column: Metrosep ASUPP7 - 250 (4.0 mm inner diameter × 250 mm). The detector uses a Metrohm Model 819 conductivity detector. The ion chromatography detection conditions are as follows:

[0208] Column temperature: 45 °C; Flow rate: 0.7 mL / min; Eluent: 10 mM sodium carbonate (Na2CO3) solution, 35% v / v acetonitrile; Injection volume: 100 μL; Detection range and full scale of conductivity detector: 100 μS / s.

[0209] Mass spectrometry was performed using an Agilent 6410 triple quadrupole mass spectrometer. The mass spectrometry detection conditions are as follows:

[0210] Mass spectrometry type is electrospray ionization source (ESI); Nebulizer pressure: 45 psig; Dry gas flow rate: 12 L / min; Dry gas temperature: 350 °C; Capillary voltage: 1750 V; Fragmentation voltage: 120 V; Collision energy: 30 V.

[0211] Synthesis Examples

[0212] Compound (Also denoted as LiSF3C2O5 in this article) synthesis

[0213] Mix SO2F2 with anhydrous oxalic acid, add P2O5 to the above mixture for dehydration to form anhydride, separate the obtained mixture by column chromatography to obtain fluorosulfuric oxalic anhydride, and mix it with LiF and stir to form a salt to obtain the above compound.

[0214] MS m / z (ESI): 173 [M] - ;

[0215] 19 F NMR (471 MHz, CDCl3) δ: 65.

[0216] Compound (Also denoted as LiSFC4O9 in this article) synthesis

[0217] Mix SO3 with anhydrous oxalic acid, add P2O5 to the above mixture for dehydration to form anhydride, separate the obtained mixture by column chromatography to obtain fluorosulfuric oxalic anhydride, and mix it with LiF and stir to form a salt to obtain the above compound.

[0218] MS m / z (ESI): 207 [M] - ;

[0219] 19 F NMR (471 MHz, CDCl3) δ: 72.

[0220] Compound (Also denoted as TBASF3C2O5 in this article) was synthesized by a method similar to that of compound similar.

[0221] MS m / z (ESI): 173 [M] - ;

[0222] 19 19F NMR (471 MHz, CDCl3) δ: 65.

[0223] Compound (also denoted herein as TBASFC4O9) is synthesized by a method similar to that of Compound .

[0224] MS m / z (ESI): 207 [M] - ;

[0225] 19 19F NMR (471 MHz, CDCl3) δ: 72.

[0226] Preparation Examples

[0227] Preparation of the positive electrode of the secondary battery

[0228] The positive electrode of the secondary battery of the present invention can be prepared by the following method

[0229] The positive electrode active material, acetylene black, and polyvinylidene fluoride (PVDF) are added to an anhydrous N-methylpyrrolidone solvent and mixed to form a slurry, where the mass ratio of the positive electrode active material, acetylene black, and polyvinylidene fluoride (PVDF) is 90:5:5. The obtained slurry is coated on one side of an aluminum foil pre-coated with a conductive aid, where the thickness of the aluminum foil is 15 μm. After drying the aluminum foil, the thickness of the aluminum foil is extended to 80 μm using a roll press. Subsequently, the obtained electrode sheet is cut into the following shape, where the active material layer is 30 mm wide and 40 mm long, and the uncoated part is 5 mm wide and 9 mm long. The obtained product is the positive electrode sheet of the secondary battery.

[0230] Preparation of the negative electrode of the secondary battery

[0231] The negative electrode of the secondary battery of the present invention can be prepared by the following method.

[0232] Mix the negative electrode active material, an aqueous dispersion of sodium carboxymethyl cellulose with a mass fraction of 1%, and an aqueous dispersion of styrene-butadiene rubber with a mass fraction of 50% to make a slurry, where the mass ratio of the negative electrode active material, the aqueous dispersion of sodium carboxymethyl cellulose, and the aqueous dispersion of styrene-butadiene rubber is 98:100:2. Coat the obtained slurry on one side of a copper foil with a thickness of 10 μm. After drying the copper foil, roll it with a roll press, and cut the obtained electrode sheet into the following shape, where the active material layer is 30 mm wide and 40 mm long, and the uncoated part is 5 mm wide and 9 mm long. The obtained product is the negative electrode sheet of the secondary battery.

[0233] Preparation of the electrolyte for the secondary battery

[0234] The electrolyte for the secondary battery of the present invention can be prepared by the following method.

[0235] In an atmosphere of dry argon, take different non-aqueous solvents and mix them. Subsequently, add a sufficiently dried lithium salt and additives to the mixed solvent, and add other additives to obtain a non-aqueous electrolyte.

[0236] Preparation of the secondary battery

[0237] The secondary battery of the present invention can be prepared by the following method.

[0238] Stack the positive electrode sheet, the negative electrode sheet, and a separator made of polyethylene in the order of negative electrode, separator, positive electrode, separator, and end with the negative electrode to obtain a bare battery cell. Thermally press the bare battery cell so that the PVDF on the surface of the separator bonds the electrode sheets together. After welding the tabs of the thermally pressed bare battery cell, place it in a pre-punched aluminum-plastic film and perform heat melting and encapsulation to obtain a pre-encapsulated battery with a liquid injection port. Place the pre-encapsulated battery in a vacuum furnace for sufficient baking and drying, then inject a certain amount of electrolyte from the liquid injection port, and encapsulate the liquid injection port in a vacuum environment to obtain the secondary battery of the present invention.

[0239] Prepare the secondary batteries of Examples 1-9 and Comparative Examples 1-3 according to the above method.

[0240] Example 1

[0241] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 14.5% by weight. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1.5% of LiPF2O2 (lithium difluorophosphate) and 1% of LiFSI (lithium bis(fluorosulfonyl)imide) as the second lithium salts, 4% of VC (vinylene carbonate), 0.5% of PS (1,3-propane sultone), and 1% of LiSF3C2O5 to obtain the non-aqueous electrolyte. A secondary battery is prepared according to the above method, wherein the positive electrode active material is LiNi 0.65 Co 0.15 Mn 0.2 O2, and the negative electrode active material is artificial graphite.

[0242] Example 2

[0243] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 14.5% by weight. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1.5% of LiPF2O2 (lithium difluorophosphate) and 1% of LiFSI (lithium bis(fluorosulfonyl)imide) as the second lithium salts, 4% of VC (vinylene carbonate), 0.5% of PS (1,3-propane sultone), 0.2% of LiSF3C2O5, and 0.8% of TBASF3C2O5 to obtain the non-aqueous electrolyte. A secondary battery is prepared according to the above method, wherein the positive electrode active material is LiNi 0.65 Co 0.15 Mn 0.2 O2, and the negative electrode active material is artificial graphite.

[0244] Example 3

[0245] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 13.0% by weight. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1.5% of LiPF2O2 (lithium difluorophosphate) and 1% of LiFSI (lithium bis(fluorosulfonyl)imide) as the second lithium salts, 4% of VC (vinylene carbonate), 0.5% of PS (1,3-propane sultone), and 1% of LiSFC4O9 to obtain the non-aqueous electrolyte. A secondary battery is prepared according to the above method, wherein the positive electrode active material is LiNi 0.65 Co0.15 Mn 0.2 O2, and the negative electrode active material is artificial graphite.

[0246] Example 4

[0247] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 13.0 wt%. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1.5% of LiPF2O2 (lithium difluorophosphate) and 1% of LiFSI (lithium bis(fluorosulfonyl)imide) as the second lithium salts, 4% of VC (vinylene carbonate), 0.5% of PS (1,3-propane sultone), 0.2% of LiSFC4O9, and 0.8% of TBASFC4O9 to obtain a non-aqueous electrolyte. A secondary battery is prepared according to the above method, where the positive electrode active material is LiNi 0.65 Co 0.15 Mn 0.2 O2, and the negative electrode active material is artificial graphite.

[0248] Example 5

[0249] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 13.0 wt%. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1% of LiPF2O2 (lithium difluorophosphate), 1% of LiFSI (lithium bis(fluorosulfonyl)imide), and 1% of LiTFSI (lithium bis(trifluoromethylsulfonyl)amide) as the second lithium salts, 4% of DTD (ethylene sulfate), 0.5% of VC (vinylene carbonate), 1% of PS (1,3-propane sultone), 0.8% of LiSF3C2O5, and 0.2% of LiSFC4O9 to obtain a non-aqueous electrolyte. A secondary battery is prepared according to the above method, where the positive electrode active material is LiNi 0.55 Co 0.15 Mn 0.3 O2, and the negative electrode active material is artificial graphite.

[0250] Example 6

[0251] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:6:1. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 13.5 wt%. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1% of LiPF2O2 (lithium difluorophosphate), 0.5% of LiODFP (lithium bis(oxalato)difluorophosphate), and 0.4% of LiBF4 as the second lithium salt, 0.5% of DTD (vinyl sulfite), 4% of PC (acrylate), 0.5% of VC (vinylene carbonate), 1% of PS (1,3-propane sultone), 0.5% of LiSF3C2O5, and 0.5% of LiSFC4O9, where the positive electrode active material is LiNi 0.55 Co 0.15 Mn 0.3 O2, and the negative electrode active material is natural graphite.

[0252] Example 7

[0253] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 14 wt%. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1% of LiPF2O2 (lithium difluorophosphate) and 0.5% of LiODFB (lithium difluorooxalate borate) as the second lithium salt, 3% of FEC (fluoroethylene carbonate), 1% of PS (1,3-propane sultone), 3% of LiSF3C2O5, and 3% of LiSFC4O9, where the positive electrode active material is LiNi 0.8 Co 0.1 Mn 0.1 O2, and the negative electrode active material is silicon-oxygen composite artificial graphite.

[0254] Example 8

[0255] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:4:3. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 14 wt%. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1% of LiPF2O2 (lithium difluorophosphate), 1.5% of LiFSI (lithium bis(fluorosulfonyl)imide), 0.1% of LiBF4, and 1% of LiTFSI (lithium bis(trifluoromethylsulfonyl)amide) as the second lithium salts, 4% of DMC (dimethyl carbonate), 0.5% of VC (vinylene carbonate), 1.5% of PS (1,3-propane sultone), 0.5% of LiSF3C2O5, and 0.5% of LiSFC4O9, where the positive electrode active material is LiNi 0.65 Co 0.15 Mn 0.3 O2, and the negative electrode active material is natural graphite.

[0256] Example 9

[0257] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 10 wt%. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1% of LiFSI (lithium bis(fluorosulfonyl)imide) and 1% of LiTFSI (lithium bis(trifluoromethylsulfonyl)amide) as the second lithium salts, 2% of VC (vinylene carbonate), 1% of PS (1,3-propane sultone), 2% of LiSF3C2O5, and 2% of LiSFC4O9, where the positive electrode active material is LiNi 0.55 Co 0.1 Mn 0.35 O2, and the negative electrode active material is artificial graphite.

[0258] Comparative Example 1

[0259] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Sufficiently dried first lithium salt LiPF6 is added to make its content in the non-aqueous electrolyte 13 wt%. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1.5% of LiPO2F2 (lithium difluorophosphate) and 1% of LiFSI (lithium bis(fluorosulfonyl)imide) as the second lithium salts, 4% of VC (vinylene carbonate), 0.5% of PS (1,3-propane sultone), where the positive electrode active material is LiNi 0.65 Co 0.15 Mn0.2 The cathode active material is LiNiCoMn02, and the anode active material is artificial graphite.

[0260] Comparative Example 2

[0261] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Sufficiently dried first lithium salt LiPF6 is added so that its content in the non-aqueous electrolyte is 14 wt%. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1% of LiPO2F2 (lithium difluorophosphate) and 0.5% of LiODFB (lithium difluorooxalate borate) as the second lithium salts, 3% of FEC (fluoroethylene carbonate), 1% of PS (1,3-propane sultone), where the cathode active material is LiNi 0.8 Co 0.1 Mn 0.1 O2, and the anode active material is silicon-oxygen composite artificial graphite.

[0262] Comparative Example 3

[0263] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:6:1. Sufficiently dried first lithium salt LiPF6 is added so that its content in the non-aqueous electrolyte is 13.5 wt%. Based on the total weight of the non-aqueous electrolyte, the following components are added respectively: 1% of LiPF2O2 (lithium difluorophosphate), 0.5% of LiODFP (lithium bis(oxalato)difluorophosphate), and 0.4% of LiBF4 as the second lithium salts, 0.5% of DTD (ethylene sulfate), 4% of PC (acrylate), 0.5% of VC (vinylene carbonate), 1% of PS (1,3-propane sultone), where the cathode active material is LiNi 0.55 Co 0.15 Mn 0.3 O2, and the anode active material is natural graphite.

[0264] Comparative Example 4

[0265] The preparation of the secondary battery of Comparative Example 4 refers to Example 1, where 1% of LiSC4O8 is used as an additive to replace LiSF3C2O5 in Example 1.

[0266] Comparative Example 5

[0267] The preparation of the secondary battery of Comparative Example 5 refers to Example 1, where 1% of LiSF2C2O4 is used as an additive to replace LiSF3C2O5 in Example 1.

[0268] Comparative Example 6

[0269] The preparation of the secondary battery of Comparative Example 6 was referred to Example 9, where the content of LiPF6 was 12% by weight, and 1% of LiSC4O8 and 1% of LiSF2C2O4 were used as additives to replace LiSF3C2O5 and LiSFC4O9 of Example 9.

[0270] Tests

[0271] The secondary battery of the present invention can be tested by the following method.

[0272] (1) Initial discharge capacity and cycle test of the secondary battery

[0273] The prepared battery was subjected to formation aging treatment and then placed on a fixture. At 25°C, the activated battery was charged to 4.3V at a current of 1C and held at a constant voltage until the current reached 0.05C, and then discharged to 2.8V at a current of 1C. The discharge capacity was recorded. The initial DCR of the battery was recorded in the first cycle of discharge. Subsequently, the cycle test was carried out until the discharge capacity of the battery reached 80% of the capacity in the first cycle and then stopped. The DCR, DCR growth rate, number of cycles for the battery to reach 80% SOH (State of Health of the battery), and change in gas production volume after the cycle were recorded.

[0274] The change in the direct current resistance and the gas production volume of the secondary battery were measured by the following methods respectively:

[0275] (i) Test of the direct current resistance (DCR) of the secondary battery

[0276] At a specified temperature, when the battery was discharged at a current of 1C to 50% SOC (State of Charge, reflecting the remaining capacity of the battery), the current was increased to 4C and maintained for 30s. The difference between the updated stable voltage and the original platform voltage was detected. The ratio of this value to the 3C current value was the direct current resistance of the battery. The DCR after the cycle was compared with the DCR at the start of the cycle to obtain the DCR growth rate.

[0277] (ii) Test of the change in gas production volume of the secondary battery

[0278] The secondary battery was completely immersed in water at 25°C after being fixed with a thin string, and the weight difference before and after immersion was recorded. The volume difference was obtained by converting according to the density of water at 25°C.

[0279] (2) Test of the capacity recovery rate of the secondary battery at 60°C

[0280] After aging Examples 5, 6, 7, Comparative Examples 2 and 3, at 25 °C, the activated battery was charged to 4.3 V at a current of 1 C and held at a constant voltage until the current reached 0.05 C. Then, the secondary battery was placed in an environment at 60 °C for 60 days, and its capacity recovery rate after 60 days was recorded.

[0281] (3) Cycle test of the secondary battery at 60 °C

[0282] After aging Examples 5, 6 and 7, Comparative Examples 2 and 3, at 60 °C, the activated battery was charged to 4.25 V at a current of 1 C and held at a constant voltage until the current reached 0.05 C, and then discharged at 1 C to 3.0 V, and the discharge capacity was recorded. The initial DCR of the battery was recorded during the first cycle of discharge. Subsequently, the cycle test was carried out until the discharge capacity of the battery reached 80% of the capacity of the first cycle and then stopped. The DCR, DCR growth rate and change in gas generation volume of the battery after the cycle were recorded.

[0283] (4) Cycle test of the secondary battery at -30 °C

[0284] After formation and aging of Example 6 and Comparative Example 3, at -30 °C, the activated battery was charged to 4.25 V at a current of 1 C and held at a constant voltage until the current reached 0.05 C, and then discharged at 1 C to 3.0 V, and the discharge capacity was recorded. The initial DCR of the battery was recorded during the first cycle of discharge. Subsequently, the cycle test was carried out until the discharge capacity of the battery reached 80% of the capacity of the first cycle and then stopped. The DCR growth rate of the battery after the cycle was recorded.

[0285] Results

[0286] Table 1 shows the results of the initial discharge capacity test, cycle test, direct current resistance (DCR) test, and gas generation volume change test of the secondary batteries of Examples 1 - 9. Table 2 shows the results of the capacity recovery rate test of the secondary batteries of Examples 5 - 7 at 60 °C and the DCR growth rate test at -30 °C.

[0287] Table 1

[0288] Examples <![CDATA[SOH Number of Turns a > Initial DCR (mohm) <![CDATA[DCR growth rate b > Growth Rate of Gas Generation Volume 1 2212 1.22 24％ 8％ 2 2209 1.32 29％ 10％ 3 2131 1.25 24％ 9％ 4 2125 1.35 27％ 10％ 5 2198 1.23 28％ 5％ 6 2501 1.15 25％ 3％ 7 2004 1.2 20％ 11％ 8 2293 1.13 24％ 6％ 9 1995 1.17 27％ 7％

[0289] a Number of cycles for the battery to reach 80% SOH at 25 °C; b DCR growth rate at the end of the cycle

[0290] As shown in Table 1, the secondary batteries of Examples 1-9 have a low initial DC resistance, only about 1.13-1.35 mohm. After charge and discharge cycles, the growth rate of the DC resistance of the secondary batteries of Examples 1-9 is also relatively reduced, only about 20%-about 29%, and the growth rate of the gas volume generated by the secondary batteries is even lower, only about 3%-about 11%. Thus, with the compound of formula (I) as an additive, the secondary battery of the present invention has good stability. After multiple charge and discharge cycles, the DC resistance of the secondary battery only increases slightly, and the volume change of the generated gas is not significant. In addition, when the secondary batteries of Examples 1-9 reach 80% SOH, they have a high number of cycles, which is 1995-2501. Thus, with the compound of formula (I) as an additive, the secondary battery of the present invention has a long service life.

[0291] Table 2

[0292] Examples <![CDATA[DCR growth rate a > <![CDATA[Capacity recovery rate b > <![CDATA[Gas production volume growth rate c > <![CDATA[DCR growth rate d > 5 22％ 97％ 7％ 6 15％ 98％ 4％ 10％ 7 21％ 92％ 6％

[0293] a DCR growth rate after 60 days at 60 °C; b Capacity recovery rate after 60 days at 60 °C; c Gas volume growth rate after 60 days at 60 °C; d DCR growth rate at the end of -30 °C cycle

[0294] In Examples 5-7, other additives DTD (ethylene sulfate), PC (acrylate) or FEC (fluoroethylene carbonate) are added and act together with the compound of formula (I), which is beneficial to improving the high-temperature stability or low-temperature stability of the battery. As shown in Table 2, the secondary battery of the present invention has excellent high-temperature performance. After multiple charge and discharges at high temperature (e.g., about 60 °C), the growth rate of the DC resistance of the secondary battery is only 15%-22%, the capacity recovery rate can reach 92%-98%, and the gas volume growth rate is only 4-7%. And after multiple charge and discharges at low temperature (e.g., about -30 °C), the growth rate of the DC resistance of the secondary battery is only 10%. Thus, with the compound of formula (I) as an additive and acting together with other additives, it is beneficial to further improve the high-temperature and low-temperature stability of the secondary battery.

[0295] Table 3 shows the test results of the initial discharge capacity, cycle test, direct current resistance (DCR) test, and gas volume change test of the secondary battery of the comparative example. The test conditions are the same as those used in Table 1.

[0296] Table 3

[0297] Comparative Examples <![CDATA[SOH Number of Turns a > Initial DCR (mohm) <![CDATA[DCR growth rate b > Growth Rate of Gas Generation Volume 1 1297 1.43 40％ 37％ 2 573 1.59 70％ 90％ 3 1567 1.28 36％ 6％ 4 890 1.41 31％ 16％ 5 721 1.43 32％ 21％ 6 873 1.43 29％ 18％

[0298] a Number of cycles for the battery to reach 80% SOH at 25 °C;b DCR growth rate at the end of the cycle

[0299] As shown in Table 3, compared with Examples 3 and 7, Compounds of Formula (I) were not added in Comparative Examples 1 and 2. When the secondary batteries reached 80% SOH, the number of cycles they had was only 573 - 1567, far lower than those of Examples 1 - 9. Thus, it can be seen that as an additive, the Compound of Formula (I) can effectively improve the service life of secondary batteries. In addition, compared with Examples 1 - 9, Comparative Examples 1 - 2 had relatively higher DCR, and the battery working efficiency decreased. Moreover, Comparative Examples 1 - 2 had significantly increased DCR growth rate and gas production volume growth rate. Thus, it can be seen that as an additive, the Compound of Formula (I) can effectively improve the stability of secondary batteries, and reduce the DCR growth rate and gas production volume growth rate.

[0300] As shown in Table 3, compared with Example 1, 1% of LiSC4O8, 1% of LiSF2C2O4, 1% of LiSC4O8 and 1% of LiSF2C2O4 were respectively added in Comparative Examples 4 - 6 as additives for secondary batteries. First, when the secondary batteries reached 80% SOH, the number of cycles they had was only 721 - 890, far lower than those of the compounds in the examples. Thus, it can be seen that compared with the additives for secondary batteries in the prior art, the Compound of Formula (I) in this application can effectively improve the service life of secondary batteries as an additive. In addition, compared with the compounds in the examples, Comparative Examples 4 - 6 had relatively higher DCR, and the battery working efficiency decreased. Moreover, Comparative Examples 4 - 6 had relatively higher gas production volume growth rate. Thus, it can be seen that compared with the additives for secondary batteries in the prior art, the Compound of Formula (I) in this application can effectively improve the stability of secondary batteries and reduce the gas production volume growth rate.

[0301] Table 4 shows the test results of the DCR growth rate, capacity recovery rate and gas production volume growth rate of the secondary batteries of Comparative Examples 2 and 3 at 60 °C, and the DCR growth rate test result of the secondary battery of Comparative Example 3 at - 30 °C. The test conditions were the same as those used in Table 2.

[0302] Table 4

[0303] Comparative Examples <![CDATA[DCR growth rate a > <![CDATA[Capacity recovery rate b > <![CDATA[Gas production volume growth rate c > <![CDATA[DCR growth rate d > 2 67 84 23 3 30 92 15 50

[0304] a DCR growth rate after 60 days at 60 °C; b Capacity recovery rate after 60 days at 60 °C; c Gas production volume growth rate after 60 days at 60 °C; d DCR growth rate at the end of the cycle at - 30 °C

[0305] As shown in Table 4, compared with Example 7, after the secondary battery of Comparative Example 2 was placed in an environment of 60 °C for 60 days, the secondary battery had a significantly higher DCR growth rate and a relatively lower capacity recovery rate. Therefore, the compound of formula (I) as an additive can improve the high-temperature performance of the secondary battery. In addition, compared with Example 6, in Comparative Example 3, after multiple charge and discharge cycles at low temperature (e.g., about -30 °C), the growth rate of the DC resistance of the secondary battery was 50%, which was much higher than that of Example 6. Thus, it can be seen that the compound of formula (I) as an additive can improve the low-temperature performance of the secondary battery.

[0306] The above are only specific embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent transformation made using the present invention, directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. An additive for non-aqueous electrolyte, which comprises a compound represented by formula (I): Characterized in that, M is a counter cation; m is an integer from 1 to 3; X1, X2, X3 and X4 are each independently selected from oxygen and sulfur; R1 is selected from halogen, halo-C 1-10 alkyl and halo-C 3-10 cycloalkyl; R2 and R3 are each independently selected from halogen, halo-C 1-10 alkyl and halo-C 3-10 cycloalkyl; or R2 and R3 are each independently selected from oxygen or sulfur, and R2 and R3 together with the atoms connected to them jointly form a moiety represented by formula (II), wherein X5 and X6 are each independently selected from oxygen and sulfur.

2. The additive for non-aqueous electrolyte according to claim 1, characterized in that, X1, X2, X3 and X4 are oxygen.

3. The additive for non-aqueous electrolyte according to claim 1, characterized in that, R1 is selected from halogens.

4. The additive for non-aqueous electrolyte according to claim 3, characterized in that, R1 is selected from fluorine, chlorine and bromine.

5. The additive for non-aqueous electrolyte according to claim 4, characterized in that, R1 is fluorine.

6. The additive for non-aqueous electrolyte according to claim 1, characterized in that, R2 and R3 are each independently selected from halogens; or R2 and R3 are each independently oxygen, and R2 and R3 together with the atoms connected to them jointly form a moiety represented by formula (II), wherein X5 and X6 are each independently oxygen.

7. The additive for non-aqueous electrolyte according to claim 6, characterized in that, R2 and R3 are each independently selected from fluorine, chlorine and bromine.

8. The additive for non-aqueous electrolyte according to claim 7, characterized in that, R2 and R3 are fluorine.

9. The additive for non-aqueous electrolyte according to claim 1, characterized in that, The counter cation is a metal cation or a quaternary amine group.

10. The additive for non-aqueous electrolyte according to claim 9, characterized in that, The metal cation is selected from lithium ion, sodium ion, potassium ion, calcium ion, magnesium ion and combinations thereof; The quaternary amine group is selected from tetramethylamine, tetraethylamine, tetrapropylamine, tetrabutylamine.

11. The additive for non-aqueous electrolyte according to claim 10, characterized in that, The metal cation is lithium ion; The quaternary amine group is tetrabutylamine.

12. The additive for non-aqueous electrolyte according to any one of claims 1-11, characterized in that, The compound of formula (I) is selected from and combinations thereof, wherein M and m are as defined in any one of claims 1-11.

13. The additive for non-aqueous electrolyte according to any one of claims 9-11, characterized in that, The compound of formula (I) is selected from and combinations thereof, M m+ is a metal cation or quaternary ammonium group as defined in any one of claims 9-11, and m is an integer from 1 to 3.

14. The additive for non-aqueous electrolyte according to claim 1, characterized in that, The compound of formula (I) is selected from and combinations thereof.

15. A non-aqueous electrolyte, which comprises the additive for non-aqueous electrolyte according to any one of claims 1-14.

16. The non-aqueous electrolyte according to claim 15, characterized in that, Based on the total weight of the non-aqueous electrolyte, the content of the compound represented by formula (I) in the non-aqueous electrolyte is 0.1-10% by weight.

17. The non-aqueous electrolyte according to claim 16, characterized in that, Based on the total weight of the non-aqueous electrolyte, the content of the compound represented by formula (I) in the non-aqueous electrolyte is 0.2-6% by weight.

18. The non-aqueous electrolyte according to claim 17, wherein based on the total weight of the non-aqueous electrolyte, the content of the compound represented by formula (I) in the non-aqueous electrolyte is 1% by weight.

19. The non-aqueous electrolyte according to claim 15, wherein the non-aqueous electrolyte further comprises a non-aqueous solvent, wherein the non-aqueous solvent is selected from cyclic esters, chain esters, and combinations thereof.

20. The non-aqueous electrolyte according to claim 19, wherein the cyclic ester is a cyclic carbonate; and / or the chain ester is a chain carbonate.

21. The non-aqueous electrolyte according to claim 20, wherein the cyclic carbonate is selected from ethylene carbonate, propylene carbonate, butylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one, trans- or cis-4,5-difluoro-1,3-dioxolan-2-one, fluoroethylene carbonate, vinylene carbonate, ethylene vinylene carbonate, and combinations thereof.

22. The non-aqueous electrolyte according to claim 21, wherein the cyclic carbonate is selected from ethylene carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, butylene carbonate, and combinations thereof.

23. The non-aqueous electrolyte according to claim 22, wherein the cyclic carbonate is selected from ethylene carbonate, vinylene carbonate, fluoroethylene carbonate, and combinations thereof.

24. The non-aqueous electrolyte according to claim 19, characterized in that, The chain ester is selected from methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, ethyl methyl carbonate, methyl propyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl propyl carbonate, dipropyl carbonate, and combinations thereof.

25. The non-aqueous electrolyte according to claim 24, wherein the chain ester is selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and combinations thereof.

26. The non-aqueous electrolyte according to claim 15, wherein the non-aqueous electrolyte further comprises a first lithium salt; the first lithium salt is selected from LiPF6, LiBF4, LiBCl4, LiAsF6, LiClO4, LiAlO2, LiF, LiCl, LiBr, LiI, LiSbF6, and combinations thereof.

27. The non-aqueous electrolyte according to claim 26, wherein the first lithium salt is selected from LiPF6, LiBF4, and combinations thereof.

28. The non-aqueous electrolyte according to claim 26, wherein the non-aqueous electrolyte further comprises a second lithium salt, which is selected from lithium salts containing a P=O structure, lithium salts containing a -S(=O)2- structure, lithium salts with a boron oxalate complex as an anion, and combinations thereof.

29. The non-aqueous electrolyte according to claim 28, wherein the second lithium salt is selected from LiPO2F2, Li2PO3F, LiODFB, LiODFP, LiBOB, LiTFSI, LiFSI, and combinations thereof.

30. The non-aqueous electrolyte according to claim 29, wherein The second lithium salt is selected from LiPO2F2, LiODFB, LiODFP, LiBOB, LiTFSI, LiFSI and combinations thereof.

31. The non-aqueous electrolyte according to claim 29, wherein the total content of the first lithium salt and the second lithium salt is 10-20% by weight.

32. The non-aqueous electrolyte according to claim 31, wherein the total content of the first lithium salt and the second lithium salt is 11-17.6% by weight.

33. The non-aqueous electrolyte according to claim 31, wherein the total content of the first lithium salt and the second lithium salt is 15.4-17.5% by weight.

34. The non-aqueous electrolyte according to claim 31, wherein the content of the first lithium salt is 8-16% by weight.

35. The non-aqueous electrolyte according to claim 31, wherein the content of the first lithium salt is 10-15% by weight.

36. The non-aqueous electrolyte according to claim 31, wherein the content of the first lithium salt is 13.5-14.5% by weight.

37. The non-aqueous electrolyte according to claim 15, characterized in that, The non-aqueous electrolyte further optionally contains one or more additives selected from: vinylene carbonate, fluoroethylene carbonate, dimethyl carbonate, 1,3-propane sultone, ethylene sulfate, propylene carbonate.

38. The non-aqueous electrolyte according to claim 37, characterized in that, The content of the additive is 0-10% by weight.

39. The non-aqueous electrolyte according to claim 38, wherein The content of the additive is 2-7% by weight.

40. The non-aqueous electrolyte according to claim 39, characterized in that, The content of the additive is 4-6% by weight.

41. An electricity storage device, wherein the electricity storage device contains the additive for non-aqueous electrolyte according to any one of claims 1-14 or the non-aqueous electrolyte according to any one of claims 15-40.

42. The electricity storage device according to claim 41, wherein the electricity storage device is a secondary battery.

43. An electric device, wherein the electric device contains the electricity storage device according to claim 41.

44. The electric device according to claim 43, wherein the electric device is selected from electric vehicles, electric two-wheelers and power storage systems.

45. The electric device according to claim 44, wherein the electric vehicle is selected from electric cars, hybrid cars, plug-in hybrid cars.

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