Electrolyte for secondary battery, secondary battery, battery module, battery pack, and power consumption device

Abstract

The present application provides a secondary battery electrolyte, a secondary battery, a battery module, a battery pack, and a power consumption device. The secondary battery electrolyte includes a fluoroether-based solvent and an additive, the additive including one or more of an ionic liquid-based additive, an amide compound-based additive, a cation-shielding additive, and an alloy-based additive. The present application adds one or more of the ionic liquid-based additive, the amide compound-based additive, the cation-shielding additive, and the alloy-based additive to the fluoroether-based solvent-containing electrolyte, thereby significantly improving the interfacial stability of the secondary battery, improving the cycle performance and storage stability of the secondary battery, and enhancing the overall safety of the secondary battery.

Description

[Technical Field]

[0001] The present application relates to the field of secondary battery technology, and in particular to an electrolyte for secondary batteries, secondary batteries, battery modules, and power consuming devices. [Background technology]

[0002] In recent years, secondary batteries have been widely applied in energy storage power systems such as hydroelectric, thermal, wind and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. As the applications of secondary batteries become more widespread, higher requirements are being placed on their energy density, cycle performance, etc.

[0003] Electrolytes are a medium for transmitting ions between positive and negative electrodes. As an important component of secondary batteries, they play a crucial role in determining the battery's power supply performance, cycle life, safety, etc. Liquid electrolytes, commonly referred to as electrolytic solutions, often have good ionic conductivity, imparting excellent kinetic performance to batteries. However, they are highly reactive and prone to side reactions, particularly with metal anodes, preventing them from effectively improving the battery's cycle performance and storage performance. Therefore, further optimization of the electrolyte composition is necessary to provide an electrolyte that has stable electrochemical properties and can improve the overall electrochemical performance of secondary batteries. Summary of the Invention

[0004] The present application has been made in view of the above-mentioned problems, and its purpose is to provide an electrolyte for secondary batteries, which is obtained by adding one or more of an ionic liquid additive, an amide compound additive, a cation shielding additive, and an alloy additive to a fluoroether solvent obtained by directly substituting ether molecules with fluorine, to provide an electrolyte having stable electrochemical properties, and secondary batteries manufactured using this electrolyte have improved interface stability, high-temperature performance, cycle performance, and storage stability.

[0005] A first aspect of the present application provides an electrolyte for a secondary battery, the electrolyte for the secondary battery comprising a fluoroether-based solvent and an additive, the additive comprising one or more of an ionic liquid-based additive, an amide compound-based additive, a cation-shielding additive, and an alloy-based additive. In any of the embodiments, the fluoroether-based solvent is obtained after directly substituting fluorine for hydrogen on a carbon of a corresponding ether-based molecule.

[0006] In any of the embodiments, the cation of the ionic liquid additive comprises one or more of a nitrogen-containing onium ion and a phosphorus-containing onium ion, and the anion of the ionic liquid additive comprises one or more of a halogen ion, a phosphate ion, a borate ion, a sulfonylimide compound anion, and a sulfonamide compound anion.

[0007] By adding one or more additives selected from the group consisting of an ionic liquid additive, an amide compound additive, a cation shielding additive, and an alloy additive to an electrolyte solution containing a fluoroether solvent, the interface stability of the secondary battery can be significantly improved, the cycle performance and storage stability of the secondary battery can be improved, and the safety of the secondary battery as a whole can be enhanced.

[0008] In any embodiment, the cation of the ionic liquid based additive comprises one or more of 1-butyl-3-methylimidazolium, 1-benzyl-3-methylimidazolium, 3-methyl-1-ethoxycarbonylmethylimidazolium, 1-alkyl-3-methylimidazolium, 1-[(trimethylsilyl)methyl]benzotriazolium, N-alkyl-N-methylpiperidinium, 5-azoniaspiro[4.4]nonane, trihexyl(tetradecyl)phosphine ion, tetrabutylphosphine ion, n-butyl-N-methylpyrrolidinium, and optionally 1-benzyl-3-methylimidazolium or 1-alkyl-3-methylimidazolium.

[0009] In any embodiment, the anion of the ionic liquid based additive comprises one or more of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, dicyandiamide, bis(fluorosulfonyl)amide, bis(trifluoromethylsulfonyl)amide, bis(fluorosulfonyl)imide, and bis(trifluoromethylsulfonyl)imide, and optionally one or more of chloride, bis(fluorosulfonyl)amide, bis(trifluoromethylsulfonyl)amide, bis(fluorosulfonyl)imide, and bis(trifluoromethylsulfonyl)imide.

[0010] In any embodiment, the ionic liquid based additive comprises one or more selected from 1-butyl-3-methylimidazole-bis(fluorosulfonyl)imide salts, 1-butyl-3-methylimidazole-bis(trifluoromethylsulfonyl)amide salts, 1-benzyl-3-methylimidazole-bis(fluorosulfonyl)imide salts, 1-benzyl-3-methylimidazole-bis(trifluoromethylsulfonyl)amide salts, 1-alkyl-3-methylimidazole-bis(fluorosulfonyl)imide salts, 1-alkyl-3-methylimidazole-bis(trifluoromethylsulfonyl)amide salts, 1-alkyl-3-methylimidazole-chlorine salts, and N-alkyl-N-methylpiperidine-tetrafluoroborate.

[0011] In any embodiment, the amide compound additive comprises one or more of the compounds shown in Formula I, Formula II, or Formula III: JPEG2025541546000002.jpg25165 JPEG2025541546000003.jpg28165 JPEG2025541546000004.jpg30165Here, R1 to R9 are each independently selected from hydrogen, a silyl group, a ketocarbonyl group, a C1-C3 alkyl group that is unsubstituted or substituted with at least one fluorine atom, and an aromatic group that is unsubstituted or substituted with at least one fluorine atom.

[0012] In any embodiment, the amide compound additive comprises one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylacetoacetamide, 1,1,1-trifluorofluoro-N,N-dimethylmethanesulfonamide, N,O-bis(trimethylsilyl)trifluoroacetamide, 2,3,6-trifluorobenzenesulfonamide, N,N-dimethyl-4-fluorobenzenesulfonamide, and N-methyl-N-trimethylsilane trifluoroacetamide.

[0013] In one embodiment, the cation shielding additive comprises a salt in which the cation is an alkali metal element or an alkaline earth metal element.

[0014] In any embodiment, the cation shielding system additive comprises one or more of lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, potassium hexafluorophosphate, potassium bis(oxalato)borate, potassium difluoro(oxalato)borate, potassium bis(fluorosulfonyl)imide, potassium bis(trifluoromethylsulfonyl)imide, cesium nitrate, cesium hexafluorophosphate, cesium bis(fluorosulfonyl)imide, cesium chloride, cesium bromide, calcium nitrate, strontium nitrate, and barium nitrate.

[0015] In either embodiment, the alloying additive is a compound having a Group IVA or Group VA element.

[0016] In any embodiment, the alloying additives include one or more of antimony trifluoride, antimony pentafluoride, tin difluoride, tin tetrafluoride, bismuth trichloride, and fumed silica.

[0017] In one embodiment, the weight content of the additive is 1-10% based on the total weight of the electrolyte.

[0018] When the mass content of the additive is 1-10% based on the total mass of the electrolyte, a stable SEI film can be formed at the interface between the negative electrode and the electrolyte, and an effective barrier can be established in the interfacial electric double layer to prevent the shuttle and side reactions of some ions and radicals in the electrolyte, thereby improving the interface stability, cycle performance and storage stability of the battery.

[0019] In one embodiment, the fluoroether solvent comprises a compound of formula IV or a fluorine-substituted crown ether: JPEG2025541546000005.jpg15165 wherein R7, R8, and R9 are each independently selected from hydrogen, a straight-chain or branched C1-C6 alkyl group that is unsubstituted or substituted with a fluorine or hydroxyl group, and at least one of R7, R8, and R9 contains a fluorine atom, and R7 and R9 optionally form a 5- or 6-membered saturated heterocycle together with the oxygen bonded thereto and R8 bonded to the oxygen, and at least one hydrogen atom on this ring is substituted with a fluorine or fluoroalkyl group.

[0020] In any embodiment, the fluoroether solvent is 2,2,3,3-tetrafluoro-1,4-dimethoxybutane, 2-(2-ethoxyethoxy)-1,1,1-trifluoroethane, 1,2-bis(2,2-difluoroethoxy)ethane, 2-(2-(2,2-difluoroethoxy)ethoxy)-1,1,1-trifluoroethane, 1,2-bis(2,2,2-trifluoroethoxy)ethane, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 2,2,2-trifluoroethoxy trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether, 2,2-bis(trifluoromethyl)-1,3-dioxolane, 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxopentane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxopentane, octafluorotetrahydrofuran, ethylene glycol dimethyl ether substituted with at least one fluorine atom, diethylene glycol dimethyl ether substituted with at least one fluorine atom ether, triethylene glycol dimethyl ether substituted with at least one fluorine atom, tetraethylene glycol dimethyl ether substituted with at least one fluorine atom, diethylene glycol diethyl ether substituted with at least one fluorine atom, diisopropyl ether substituted with at least one fluorine atom, dibutyl ether substituted with at least one fluorine atom, diethylene glycol dibutyl ether substituted with at least one fluorine atom, 1,4-diethoxybutane substituted with at least one fluorine atom, 15-crown ether-5 substituted with at least one fluorine atom, 12-crown ether-4 substituted with at least one fluorine atom, 18-crown ether-6 substituted with at least one fluorine atom, and optionally at least one of 2,2,3,3-tetrafluoro-1,4-dimethoxybutane and 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxopentane.

[0021] In one embodiment, the mass content of the fluoroether solvent is 20%-90% based on the total mass of the electrolyte solution.

[0022] In any embodiment, the electrolyte salt is a sodium salt, and the sodium salt includes one or more of sodium nitrate, sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium tetrafluoroyttriate, sodium hexafluoroarsenate, sodium acetate, sodium trifluoroacetate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, and sodium (n-perfluorobutylsulfonyl)imide.

[0023] In any embodiment, based on the total mass of the electrolyte solution, the mass content of the electrolyte salt is 2%-70%, and optionally 20%-70%.

[0024] When the mass content of the electrolyte salt is 2%-70% based on the total mass of the electrolyte, a stable SEI film can be formed at the interface between the negative electrode and the electrolyte, and an effective barrier can be established in the interfacial electric double layer to prevent ion and radical shuttles and side reactions, thereby improving the interfacial stability of the battery.

[0025] A second aspect of the present application provides a secondary battery, which includes the electrolyte solution of the first aspect.

[0026] In any embodiment, the secondary battery includes one or more of a lithium metal battery and a sodium metal battery.

[0027] In any of the embodiments, the secondary battery is a negative electrode-free sodium metal battery.

[0028] In any embodiment, the secondary battery includes a positive electrode plate, the positive electrode plate including a positive electrode active material, the positive electrode active material including one or more of a Prussian blue-based compound, a polyanion-type compound, and a layered oxide.

[0029] In any embodiment, the surfaces of the positive electrode active material particles have a coating layer, and the coating layer includes one or more of a carbon material (amorphous carbon, graphite, graphene), polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), aluminum oxide, zinc oxide, titanium oxide, zirconium oxide, magnesium oxide, silicon oxide, lanthanum oxide, sodium fluoride, lithium fluoride, and aluminum fluoride.

[0030] The coating layer on the surface of the positive electrode active material particles can prevent side reactions caused by direct contact between the positive electrode metal surface and the electrolyte, suppress the elution of the positive electrode transition metal, and improve the stability of the electrode / electrolyte interface.

[0031] In one embodiment, the coating layer has a thickness of 2 nm to 1000 nm.

[0032] In any embodiment, the secondary battery includes a negative electrode plate, the negative electrode plate including a negative electrode current collector and an undercoating disposed on at least one surface of the negative electrode current collector, the undercoating including one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.

[0033] In any embodiment, the negative electrode current collector includes at least one of a metal foil, a metal foam current collector, a metal mesh current collector, a carbon felt current collector, a carbon cloth current collector, a carbon paper current collector, and a composite current collector.

[0034] In any of the embodiments, the areal density of the undercoating is 2 g / m 2 -50g / m 2 is.

[0035] In one embodiment, the undercoating has a thickness of 1 μm-100 μm.

[0036] A third aspect of the present application provides a battery module, which includes the secondary battery of the second aspect.

[0037] A fourth aspect of the present application provides a battery pack, which includes the secondary battery of the second aspect or the battery module of the third aspect.

[0038] A fifth aspect of the present application provides a power consumption device, the power consumption device including at least one of the secondary battery of the second aspect, the battery module of the third aspect, or the battery pack of the fourth aspect. [Brief explanation of the drawings]

[0039] [Figure 1] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Figure 2] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 5] FIG. 5 is an exploded view of the battery pack according to the embodiment of the present application shown in FIG. 4. [Figure 6] 1 is a schematic diagram of a power consumption device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE INVENTION

[0040] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the secondary battery electrolyte, secondary battery, battery module, battery pack, and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of actually identical structures may be omitted. This is to avoid unnecessarily lengthening the following description and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0041] The "ranges" disclosed in this application are defined in the form of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values ​​and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a single range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all contemplated. In this application, unless otherwise specified, the numerical range "ab" represents a shorthand notation for any combination of real numbers from a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents that the present specification has already listed all real numbers between "0-5," and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0043] Unless otherwise stated, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0044] Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0045] Unless otherwise specified, the terms "comprise" and "include" used in this application may be open-ended or closed-ended. For example, the terms "comprise" and "include" may further include or include other components not listed, or may include or include only the listed components.

[0046] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) but B is true (or exists), or when both A and B are true (or exist).

[0047] Ether solvents are commonly used in secondary battery electrolytes, but they are not compatible with all cathode active materials, especially layered oxides with high energy density and high operating potential. The applicant unexpectedly discovered that fluorinated ether solvents, i.e., fluoroether solvents, can effectively increase the absolute value of the highest occupied molecular orbital (HOMO) of ether compounds, thereby widening the electrochemical stability window of the electrolyte and improving the operating voltage of batteries in conjunction with cathode materials with high operating potentials. However, the direct application of fluoroether solvents in secondary batteries, especially anode-free batteries, presents problems such as poor battery cycling performance and poor storage performance.

[0048] [Electrolyte for secondary batteries] Based on this, the present application provides an electrolyte solution for a secondary battery, which includes a fluoroether-based solvent and an additive, and the additive includes one or more of an ionic liquid-based additive, an amide compound-based additive, a cation-shielding additive, and an alloy-based additive.

[0049] In this specification, the term "fluoroether solvent" refers to a solvent obtained by directly fluorinating an ether solvent molecule. Unlike common fluoroether inert diluents, the fluoroether solvent in this application is used as the main solvent in the electrolyte.

[0050] As used herein, the term "additive" refers to a component present in a relatively small amount in the electrolyte solution, and may be a gas, liquid, or solid. Conceptually, the only difference between an additive, a main solvent, and an electrolyte salt is their content in the electrolyte solution, and the solvent or salt present in a relatively small amount may be collectively referred to as an additive.

[0051] As used herein, the term "ionic liquid additive" refers to a salt that is added to an electrolyte in relatively small amounts, is composed entirely of cations and anions, and is liquid at or near room temperature, which is 25°C ± 5°C.

[0052] In this specification, the term "amide compound-based additive" refers to an additive that is added to an electrolyte in a relatively small amount, It is a compound having JPEG2025541546000006.jpg30165.

[0053] As used herein, the term "cation-shielding additive" refers to a salt that is added to the electrolyte in a relatively small amount and is capable of ionizing cations, which can serve to eliminate shuttle ions and radicals that cause side reactions at the bilayer interface of the negative electrode.

[0054] As used herein, the term "alloying additive" refers to a compound that is added to the electrolyte in a relatively small amount and that contains an element that can form an alloy in the SEI film with a metal cation in the electrolyte salt.

[0055] In some embodiments, the additive comprises an ionic liquid-based additive. In some embodiments, the additive comprises an amide compound-based additive. In some embodiments, the additive comprises a cation-shielding additive. In some embodiments, the additive comprises an alloy-based additive. In some embodiments, the additive is a mixture of an ionic liquid-based additive and an amide compound-based additive. In some embodiments, the additive is a mixture of an ionic liquid-based additive and a cation-shielding additive. In some embodiments, the additive is a mixture of an ionic liquid-based additive and an alloy-based additive. In some embodiments, the additive is a mixture of an ionic liquid-based additive and an alloy-based additive. In some embodiments, the additive is a mixture of an amide compound-based additive and an alloy-based additive. In the present application, by adding one or more of an ionic liquid-based additive, an amide compound-based additive, a cation-shielding additive, and an alloy-based additive to a fluoroether-based electrolyte, it is possible to suppress the occurrence of side reactions between the metal negative electrode and the electrolyte and the resulting formation of an unstable and fragile solid electrolyte interface (SEI) film, thereby significantly improving the interface stability of the secondary battery, improving the cycle performance and storage stability of the secondary battery, and enhancing the overall safety of the secondary battery.

[0056] In some embodiments, the cation of the ionic liquid additive comprises one or more of a nitrogen-containing onium ion and a phosphorus-containing onium ion, and the anion of the ionic liquid additive comprises one or more of a halogen ion, a phosphate ion, a borate ion, a sulfonylimide-based compound anion, and a sulfonamide-based compound anion.

[0057] In some embodiments, the cation of the ionic liquid based additive comprises one or more of 1-butyl-3-methylimidazolium, 1-benzyl-3-methylimidazolium, 3-methyl-1-ethoxycarbonylmethylimidazolium, 1-alkyl-3-methylimidazolium, 1-[(trimethylsilyl)methyl]benzotriazolium, N-alkyl-N-methylpiperidinium, 5-azoniaspiro[4.4]nonane, trihexyl(tetradecyl)phosphine ion, tetrabutylphosphine ion, n-butyl-N-methylpyrrolidinium, and optionally 1-benzyl-3-methylimidazolium or 1-alkyl-3-methylimidazolium.

[0058] In some embodiments, the anion of the ionic liquid based additive comprises one or more of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, dicyandiamide anion, bis(fluorosulfonyl)amide anion, bis(trifluoromethylsulfonyl)amide anion, bis(fluorosulfonyl)imide anion, bis(trifluoromethylsulfonyl)imide, and optionally one or more of chloride, bis(fluorosulfonyl)amide anion, bis(trifluoromethylsulfonyl)amide anion, bis(fluorosulfonyl)imide anion, bis(trifluoromethylsulfonyl)imide anion.

[0059] In some embodiments, the ionic liquid based additive comprises one or more selected from 1-butyl-3-methylimidazole-bis(fluorosulfonyl)imide salts, 1-butyl-3-methylimidazole-bis(trifluoromethylsulfonyl)amide salts, 1-benzyl-3-methylimidazole-bis(fluorosulfonyl)imide salts, 1-benzyl-3-methylimidazole-bis(trifluoromethylsulfonyl)amide salts, 1-alkyl-3-methylimidazole-bis(fluorosulfonyl)imide salts, 1-alkyl-3-methylimidazole-bis(trifluoromethylsulfonyl)amide salts, 1-alkyl-3-methylimidazole-chlorine salts, and N-alkyl-N-methylpiperidine-tetrafluoroborate.

[0060] Adding an ionic liquid additive, particularly an ionic liquid containing bis(fluorosulfonyl)imide or bis(trifluoromethylsulfonyl)imide, to a fluoroether-based solvent can strengthen the SEI film formed on the negative electrode and reduce direct reaction between the negative electrode and the fluoroether solvent molecules or radicals. At the same time, the ionic liquid additive can also function to exclude solvent molecules from the electric double layer at the interface between the negative electrode and the electrolyte, thereby further reducing direct reaction between the negative electrode and the fluoroether solvent molecules or radicals, synergistically enhancing the stability at the interface between the negative electrode and the electrolyte and further improving the cycle performance and storage performance of the battery at room temperature and at high temperatures. In some embodiments, the amide compound-based additive comprises one or more of the compounds represented by Formula I, Formula II, or Formula III: JPEG2025541546000007.jpg57165Here, R1 to R9 are each independently selected from hydrogen, a silyl group, a ketocarbonyl group, a C1-C3 alkyl group that is unsubstituted or substituted with at least one fluorine atom, and an aromatic group that is unsubstituted or substituted with at least one fluorine atom.

[0061] As used herein, the term "silyl group" refers to a group consisting of -Si(R 10 )(R 11 )(R 12 ) group, where R 10 , R11 , R 12 are each independently hydrogen, substituted or unsubstituted C 1-3 The silyl group is selected from alkyl groups. Exemplary silyl groups include, but are not limited to, -SiH3, -Si(CH3)3.

[0062] As used herein, the term "ketocarbonyl group" refers to the group --R--CO--R'--, where R and R' are both hydrocarbon groups.

[0063] As used herein, the term "aromatic group" refers to an aromatic ring system in which at least one ring is aromatic, including, but not limited to, phenyl, biphenyl, indanyl, 1-naphthyl, 2-naphthyl, and tetrahydronaphthyl groups.

[0064] As used herein, the term "C1-3 alkyl group" refers to a straight or branched hydrocarbon chain group consisting solely of carbon and hydrogen atoms, the group being free of unsaturation, having from 1 to 3 carbon atoms, and being attached to the remainder of the molecule by a single bond.

[0065] As used herein, the term "substituted" means that at least one hydrogen atom of the compound or chemical moiety has been replaced by a substituent that is another chemical moiety, each of which is independently selected from the group consisting of hydroxyl, mercapto, amino, cyano, nitro, aldehyde, halogen, alkenyl, alkynyl, aryl, heteroaryl, C 1-6 Alkyl group, C 1-6 The alkoxy group is selected from the group consisting of alkoxy groups.

[0066] In some embodiments, the amide compound additive comprises one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylacetoacetamide, 1,1,1-trifluorofluoro-N,N-dimethylmethanesulfonamide, N,O-bis(trimethylsilyl)trifluoroacetamide, 2,3,6-trifluorobenzenesulfonamide, N,N-dimethyl-4-fluorobenzenesulfonamide, and N-methyl-N-trimethylsilane trifluoroacetamide.

[0067] When an amide compound-based additive is added to a fluoroether solvent, the SEI film formed on the negative electrode contains inorganic nitrides. The presence of inorganic nitrides improves the stability of the film formation, thereby significantly enhancing the electrochemical stability of the battery. At the same time, some amide compound-based additives possess Lewis basicity and can coordinate with Lewis acidic compounds in the fluoroether solvent, thereby preventing the Lewis acidic components in the electrolyte from continuing to react with the negative electrode, further improving the negative electrode interfacial stability of the battery. Due to the above roles, amide compound-based additives can significantly improve the cycle performance and storage performance of secondary batteries, especially metal batteries (including negative electrode-free batteries).

[0068] In some embodiments, the cation shielding additive comprises a salt in which the cation is an alkali metal element or an alkaline earth metal element.

[0069] As used herein, an alkali metal element is a metal element from Group IA of the periodic table other than hydrogen (H). In some embodiments, the cation shielding additive includes lithium, potassium, or cesium.

[0070] As used herein, alkaline earth metal elements are those in Group IIA of the periodic table. In some embodiments, the cation shielding additive includes the element calcium, strontium, or barium.

[0071] In some embodiments, the cation shielding system additive comprises one or more of lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, potassium hexafluorophosphate, potassium bis(oxalato)borate, potassium difluoro(oxalato)borate, potassium bis(fluorosulfonyl)imide, potassium bis(trifluoromethylsulfonyl)imide, cesium nitrate, cesium hexafluorophosphate, cesium bis(fluorosulfonyl)imide, cesium chloride, cesium bromide, calcium nitrate, strontium nitrate, barium nitrate.

[0072] The addition of a cation-shielding additive to a fluoroether solvent allows the introduction of cations different from the metal ions in the electrolyte salt. The cations in the cation-shielding additive not only eliminate shuttle ions and radicals that cause side reactions at the negative electrode interface through the electric double layer, but also induce uniform deposition and exfoliation of the metal ions in the electrolyte salt at the negative electrode. At the same time, some anions contained in the cation-shielding additive can increase the inorganic component in the SEI film and stabilize the SEI, thereby further improving the negative electrode interface stability of the battery and improving the cycle performance and storage performance of secondary batteries, particularly metal batteries (including negative electrode-free batteries). In some embodiments, the alloying additive is a compound containing a Group IVA or Group VA element.

[0073] In some embodiments, the alloying additive comprises one or more of antimony trifluoride, antimony pentafluoride, tin difluoride, tin tetrafluoride, bismuth trichloride, and fumed silica.

[0074] As used herein, the term "fumed silica," also known as gas-phase white carbon black, is amorphous nano-silicon dioxide particles.

[0075] When the above alloy additive is added to the fluoroether electrolyte, a two-layer SEI film can be formed on the negative electrode, where one SEI film is rich in an alloy component formed by the joint use of a Group IVA or Group VA element and sodium, and the other SEI film is rich in inorganic substances such as sodium fluoride, thereby not only improving the stability of the SEI film but also suppressing the formation of dendrites on the negative electrode, thereby improving the cycle performance and storage stability of the secondary battery, reducing the amount of gas generation, and contributing to improving the overall safety of the secondary battery.

[0076] In some embodiments, the weight content of the additive is 1-10% based on the total weight of the electrolyte.

[0077] In some embodiments, the mass content of the additive is optionally 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% based on the total mass of the electrolyte.

[0078] When the mass content of the additive is 1-10% based on the total mass of the electrolyte, a stable SEI film can be formed at the interface between the negative electrode and the electrolyte, and the SEI film will not be too thick to affect the ion transmission in the battery, thereby improving the overall performance of the battery.

[0079] In some embodiments, the ether solvent is a fluoroether solvent, the fluoroether solvent comprising a compound of formula IV or a crown ether substituted with a fluorine atom or a fluoroalkyl group: JPEG2025541546000008.jpg15165 wherein R7, R8, and R9 are each independently selected from hydrogen, a straight-chain or branched C1-C6 alkyl group that is unsubstituted or substituted with a fluorine or hydroxyl group, and at least one of R7, R8, and R9 contains a fluorine atom, and R7 and R9 optionally form a 5- or 6-membered saturated heterocycle together with the oxygen bonded thereto and R8 bonded to the oxygen, and at least one hydrogen atom on this ring is substituted with a fluorine or fluoroalkyl group.

[0080] As used herein, the term "C1-6 alkyl group" can be understood with reference to the definition of the term "C1-3 alkyl group."

[0081] As used herein, the term "fluoroalkyl group" refers to an alkyl group that contains at least one fluorine atom.

[0082] In some embodiments, the fluoroether solvent is 2,2,3,3-Tetrafluoro-1,4-dimethoxybutane JPEG2025541546000009.jpg171652-(2-ethoxyethoxy)-1,1,1-trifluoroethane JPEG2025541546000010.jpg111651,2-Bis(2,2-difluoroethoxy)ethane JPEG2025541546000011.jpg111652-(2-(2,2-difluoroethoxy)ethoxy)-1,1,1-trifluoroethane JPEG2025541546000012.jpg121651,2-Bis(2,2,2-trifluoroethoxy)ethane JPEG2025541546000013.jpg121651,1,1,3,3,3-Hexafluoroisopropyl methyl ether, 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether, 2,2-bis(trifluoromethyl)-1,3-dioxolane, 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxopentane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxopentane, octafluorotetrahydrofuran, ethylene glycol dimethyl ether substituted with at least one fluorine atom, diethylene glycol dimethyl ether substituted with at least one fluorine atom, triethylene glycol dimethyl ether substituted with at least one fluorine atom, tetraethylene glycol dimethyl ether substituted with at least one fluorine atom ethyl ether, diethylene glycol diethyl ether substituted with at least one fluorine atom, diisopropyl ether substituted with at least one fluorine atom, dibutyl ether substituted with at least one fluorine atom, diethylene glycol dibutyl ether substituted with at least one fluorine atom, 1,4-diethoxybutane substituted with at least one fluorine atom, 15-crown ether-5 substituted with at least one fluorine atom, 12-crown ether-4 substituted with at least one fluorine atom, 18-crown ether-6 substituted with at least one fluorine atom, and optionally at least one of 2,2,3,3-tetrafluoro-1,4-dimethoxybutane and 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxopentane.

[0083] Direct fluorination modification of ether molecules can increase the absolute value of the highest occupied molecular orbital (HOMO) of the ether, thereby widening the electrochemical stability window of the corresponding electrolyte after dissolving the electrolyte salt, improving the electrochemical stability of the electrolyte, and allowing the electrolyte to be combined with a higher potential positive electrode active material to improve the operating voltage of the secondary battery.

[0084] In some embodiments, the mass content of the fluoroether solvent is 20%-90% based on the total mass of the electrolyte.

[0085] In some embodiments, the mass content of the fluoroether solvent is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90% based on the total mass of the electrolyte solution.

[0086] Unlike using a fluoroether-based solvent as an inert diluent, the fluoroether-based solvent has a relatively high mass content in the electrolyte, and as the main solvent, it can effectively improve the electrochemical stability of the electrolyte, and when combined with a positive electrode active material with a higher potential, it can improve the working voltage of the secondary battery.

[0087] In some embodiments, the electrolyte salt is a sodium salt, including one or more of sodium nitrate, sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium tetrafluoroyttriate, sodium hexafluoroarsenate, sodium acetate, sodium trifluoroacetate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, and sodium (n-perfluorobutylsulfonyl)imide.

[0088] In some embodiments, the mass content of the electrolyte salt is 2%-70%, and optionally 20%-70%, based on the total mass of the electrolyte solution.

[0089] In some embodiments, the mass content of the electrolyte salt is 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70% based on the total mass of the electrolyte solution.

[0090] When the mass content of the electrolyte salt is 2%-70% based on the total mass of the electrolyte, the electrolytes of the present application can effectively improve the chemical stability, cycle performance, and storage performance of the battery.When the mass content of the electrolyte salt is 20%-70% based on the total mass of the electrolyte, the high concentration of the electrolyte salt can further reduce the free solvent molecules in the solvent, reduce side reactions between the solvent and the negative electrode, and improve the cycle performance, storage performance, and high-temperature performance of the battery.

[0091] [Secondary battery] In some embodiments, a secondary battery comprises the above electrolyte.

[0092] In some embodiments, the secondary battery is a lithium metal battery or a sodium metal battery.

[0093] A lithium metal battery is a battery in which the negative electrode is made of lithium metal and lithium ions are transported back and forth between the positive and negative electrodes.

[0094] A sodium metal battery is a battery in which the negative electrode is made of sodium metal and sodium ions are used to transition back and forth between the positive and negative electrodes.

[0095] In some embodiments, the secondary battery is an anode-free sodium metal battery. Anode-free sodium metal batteries do not use an anode active material, but instead use only an anode current collector as the anode. The sodium plating of the anode is completed during the initial charge, and then returns to the cathode upon discharge, achieving a charge-discharge cycle. Because they use only an anode current collector and no anode material, anode-free batteries effectively overcome the deficiencies of sodium metal batteries and can achieve higher energy densities than sodium metal anodes.

[0096] Although fluoroether solvents can effectively improve the electrochemical stability of batteries, they cause more significant side reactions in anode-free batteries. The present application adds one or more of an ionic liquid additive, an amide compound additive, a cation-shielding additive, and an alloy additive to a fluoroether solvent to form a stable SEI film at the electrode / electrolyte interface and establish an effective barrier in the interfacial electric double layer, preventing the shuttle of some ions and radicals and side reactions, thereby significantly improving the cycle performance and storage stability of anode-free sodium batteries.

[0097] In some embodiments, the secondary battery includes a positive electrode plate, the positive electrode plate including an active positive electrode material, the active positive electrode material including one or more of a Prussian blue-based compound, a polyanion-type compound, and a layered oxide.

[0098] The transition metal in the layered transition metal oxide may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Optionally, the layered transition metal oxide may be, for example, NaxMO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 <x≦1である。

[0099] Polyanionic compounds include metal ions, transition metal ions, and tetrahedral (YO4) n- It may be a compound having an anionic unit, wherein the metal ion is optionally one of sodium ion, lithium ion, potassium ion, and zinc ion, the transition metal is optionally at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y is optionally at least one of P, S, and Si, and n is (YO4) n- represents the valence of

[0100] The Prussian blue compound may be a compound containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound may be, for example, Na a Me b Me' c (CN)6, where Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn; <a≦2、0<b<1、0<c<1である。

[0101] In some embodiments, the positive electrode active material is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na(Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 )O2, Na 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 O2, Na4Fe3(PO4)2P2O7, NaFePO4, Na3V2(PO4)3, Na 1.9 It includes one or more of CoFe(CN)6, Na2NiFe(CN)6, and NaMnFe(CN)6.

[0102] Anode-free sodium metal batteries can exhibit good cycle performance in ether-based electrolytes, especially when combined with polyanion cathodes containing sodium vanadium phosphate (Na3V2(PO4)3) and sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7). Layered oxides have higher energy density, and when combined with the electrolyte of the present application, they can effectively improve the problem of low coulombic efficiency and poor cycle performance in ether-based electrolytes.

[0103] In some embodiments, the surfaces of the positive electrode active material particles have a coating layer, and the coating layer includes one or more of a carbon material (such as amorphous carbon, graphite, or graphene), polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), aluminum oxide, zinc oxide, titanium oxide, zirconium oxide, magnesium oxide, silicon oxide, lanthanum oxide, sodium fluoride, lithium fluoride, and aluminum fluoride.

[0104] The coating layer can effectively improve the stability of the positive electrode active material, reduce metal elution and particle destruction during cycling of the positive electrode active material, and effectively improve the cycle performance and storage stability of the battery.

[0105] In some embodiments, the coating layer has a thickness of 2 nm-1000 nm.

[0106] The coating layer with an appropriate thickness can play an effective improving role, and can avoid that the coating layer is too thick, which makes the resistance of the positive electrode film too high, and reduces the battery performance.

[0107] In some embodiments, a secondary battery includes a negative electrode plate, the negative electrode plate including a negative electrode current collector and an undercoating disposed on at least one surface of the negative electrode current collector, the undercoating including one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.

[0108] In some embodiments, the areal density of the undercoating is 2 g / m 2 -50g / m 2 is.

[0109] In some embodiments, the undercoating has a thickness of 1 μm-100 μm.

[0110] An undercoating within the above range effectively guides anode deposition, reduces the occurrence of anode sodium dendrites, and improves the uniformity of sodium metal deposition. Furthermore, an undercoating with the appropriate surface density and thickness can truly act as anode free, improving the energy density and safety performance of the battery.

[0111] In some embodiments, the current collector of the anode-free sodium metal battery comprises at least one of a metal foil, a metal foam current collector, a metal mesh current collector, a carbon felt current collector, a carbon cloth current collector, a carbon paper current collector, and a composite current collector.

[0112] In some embodiments, the metal foil is optionally copper foil, aluminum foil, stainless steel foil, or titanium foil, and the metal foam current collector is optionally copper foam, aluminum foam, nickel foam, or the like. The metal mesh current collector is optionally copper mesh, aluminum mesh, or stainless steel mesh. The composite current collector includes a current collector with an undercoating or a current collector with a polymer base film. The composite current collector may have a "sandwich" structure in which a polymer base film is located in the center and metal foils are provided on both sides. The composite current collector may have a metal foil provided on one side of a polymer base film. The polymer base film is optionally one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyparaphenylene terephthalamide, polypropylene ethylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, and polycarbonate. In some embodiments, the secondary battery may include an outer casing. The outer casing may be used to package the electrode assembly and electrolyte.

[0113] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The pouch may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0114] The present application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows an example of a rectangular secondary battery 5.

[0115] In some embodiments, referring to FIG. 2 , the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged within the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select the number according to actual needs.

[0116] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, with the specific number being selectable by those skilled in the art depending on the application and capacity of the battery module.

[0117] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0118] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space.

[0119] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0120] 4 and 5 show an example of a battery pack 1. Referring to FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0121] The present application also provides a power consuming device, the power consuming device including at least one of a secondary battery, a battery module, or a battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0122] The power consumption device can be selected from a secondary battery, a battery module, or a battery pack depending on its usage needs.

[0123] 6 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high power output and high energy density of the secondary battery of the power consuming device, a battery pack or battery module can be employed.

[0124] Other examples of the device may be a mobile phone, a tablet computer, a laptop computer, etc. These devices generally require a thin design and may employ a secondary battery as a power source.

[0125] Example The following examples of the present application are described. The examples described below are illustrative and are used only to interpret the present application and should not be understood as limitations on the present application. If specific techniques or conditions are not specified in the examples, they will be carried out according to the techniques or conditions described in literature in the field or according to the product specifications. If the manufacturer of the reagents or equipment used is not specified, they are all ordinary products available on the market.

[0126] Example 1 1. Manufacturing method 1. Manufacturing of positive electrode plates The positive electrode active material, carbon-coated sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7 / C), the adhesive, polyvinylidene fluoride (PVDF), and the conductive agent, conductive carbon black (Super-P), were uniformly mixed in a mass ratio of 96%:2%:2% in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. This slurry was then applied to the surface of aluminum foil using a squeeze coater according to the mass requirement per unit area of ​​the positive electrode active material, dried, and then pressed into a cold press to form a coated electrode plate at a density of 2.5 g / cm. 3 The final positive electrode plate was manufactured and obtained by cold pressing at the designed compaction density.

[0127] 2. Manufacturing of negative electrode plates Carbon nanotubes and sodium carboxymethyl cellulose were added to water in a mass ratio of 1:2 and stirred to form a uniform slurry. The slurry was coated on a negative electrode current collector, dried, and cut to obtain a negative electrode plate with a free undercoating structure, where the areal density of the undercoating was 10 g / m. 2 where the thickness of the undercoating is 5 μm.

[0128] 3. Separator A polyethylene film (PE separator) was used as the separator.

[0129] 4. Electrolyte production In a glove box (H2O<0.1 ppm, O2<0.1 ppm) under an argon gas atmosphere, 20 wt.% of bis(fluorosulfonyl)imide sodium salt was dissolved in 70 wt.% of 2,2,3,3-tetrafluoro-1,4-dimethoxybutane organic solvent, and 10 wt.% of 1,1,1-trifluorofluoro-N,N-dimethylmethanesulfonamide additive was further added and dissolved in the organic solvent, followed by stirring uniformly to obtain the electrolytic solution of Example 1.

[0130] 5. Battery manufacturing The positive electrode plate, separator, and negative electrode plate were stacked in this order, and the separator was positioned between the positive and negative electrode plates to serve as an insulator. The electrolyte was added to the resultant battery, which was then assembled into a button battery.

[0131] The specific parameters are as shown in Table 1.

[0132] In Examples 2-39, the components of the secondary battery electrolyte solution were adjusted, and the specific parameters were as shown in Table 1. Here, the mass ratio of each component of the additive in Examples 15-19 was 1:1.

[0133] In Examples 40-43, the positive electrode active material was Na[Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 ]O2, and the specific parameters of the other components are as shown in Table 1.

[0134] In Examples 44-47, the positive electrode active material was Na coated with ZrO2. 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 The specific parameters of the other components are as shown in Table 1.

[0135] In Comparative Example 1-23, the electrolyte components or positive electrode active material of the secondary battery were adjusted, and the specific parameters were as shown in Table 1. The manufacturing method was basically the same as in Example 1.

[0136] 2. Battery performance test 1) Electrochemical stability window test An electrochemical workstation was used to perform the electrolyte window test. The test temperature was 25°C, the voltage range was 1.0 to 5.0 V, and the scan rate was 0.1 mV / s. The electrolyte usage window was determined based on the starting position of the peak potential in the CV curve. All cyclic voltammetry (CV) tests in this experiment were completed on a Solartron 1470 multi-channel electrochemical workstation (UK).

[0137] 2) Room temperature / high temperature cycle performance At 25°C / 60°C and atmospheric pressure (0.1 MPa), the battery was charged at a constant current of 0.1 C to a voltage of 4 V (layered oxide cathode) or 3.7 V (sodium iron pyrophosphate cathode). It was then charged at a constant voltage of 0.01 C at 4 / 3.7 V, and then discharged at a constant current of 0.1 C to a voltage of 3.0 V. This was the first charge / discharge cycle. The battery was then charged at a constant current of 1 C to a voltage of 4 / 3.7 V, and then charged at a constant voltage of 0.1 C at 4 / 3.7 V, and then discharged at a constant current of 1 C to a voltage of 3.0 V. The capacity of the first discharge was defined as 100%, and the number of cycles at which the discharge capacity reached 80% was recorded.

[0138] 3) Room temperature / high temperature storage performance At 25°C / 60°C and atmospheric pressure (0.1 MPa), the battery was charged at a constant current of 0.1 C to 4 V (layered oxide cathode) or 3.7 V (sodium iron pyrophosphate cathode). It was then charged at a constant voltage of 0.1 C at 4 / 3.7 V until the current dropped to 0.01 C. It was then discharged at a constant current of 0.1 C to 3 V to obtain the pre-storage discharge capacity (Cd1). The sodium battery was charged at a constant current of 0.1 C at 25°C to 4 / 3.7 V, and then charged at a constant voltage of 0.01 C at 4 / 3.7 V until the current dropped to 0.01 C. The battery was charged to 100% SOC in this step. The battery was then stored in a constant temperature environment at 25°C / 60°C. The number of days of storage when the battery storage capacity retention was 80% was recorded.

[0139] The test method for discharge capacity after storage (Cdn) is to charge the battery at a constant current of 0.1C up to 4 / 3.7V at 25 / 60℃, then charge at a constant voltage of 4 / 3.7V until the current drops to 0.01C, and then discharge at a constant current of 0.1C down to 3V. The discharge capacity after n days of storage of the sodium battery is obtained and taken as Cdn.

[0140] Storage capacity retention rate = discharge capacity after storage (Cdn) / discharge capacity before storage (Cd1) * 100%.

[0141] See Tables 1 and 2 for the test results of the above examples and comparative examples.

[0142] [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4] [Table 1-5] [Table 1-6] [Table 1-7] [Table 1-8] [Table 1-9] [Table 1-10]

[0143] [Table 2-1] [Table 2-2] [Table 2-3] [Table 2-4]

[0144] As can be seen from Tables 1 and 2, the electrolytes of the anode-free sodium batteries of Examples 1 to 47 contained a fluoroether-based solvent and an additive, where the fluoroether-based solvent was the primary electrolyte solvent and the additive was selected from one or more of an ionic liquid-based additive, an amide compound-based additive, a cation-shielding additive, and an alloy-based additive. Examples 1 to 5 used an ionic liquid-based additive; Examples 6 to 8 used an amide compound-based additive; Examples 9 to 11 used a cation-shielding additive; Examples 12 to 14 used an alloy-based additive; and Examples 15 to 19 used a combination of one or more additives selected from an ionic liquid-based additive, an amide compound-based additive, a cation-shielding additive, and an alloy-based additive. Compared to Comparative Example 18, which used an ether-based solvent as the primary electrolyte, the batteries of Examples 1 to 47 exhibited a wider electrochemical stability window and the electrolytes had better electrochemical stability.

[0145] Furthermore, as can be seen from the comparison between Examples 1 to 19 and Comparative Examples 1 to 2, the comparison between Examples 20 to 27 and Comparative Examples 3 to 6, the comparison between Examples 28 to 30 and Comparative Examples 7 to 9, the comparison between Examples 35 to 39 and Comparative Examples 10 to 14, the comparison between Examples 40 to 43 and Comparative Example 15, and the comparison between Examples 44 to 47 and Comparative Example 16, by adding an additive to the electrolyte, it was possible to significantly improve the storage performance of the negative electrode-free battery at room temperature and at high temperatures.

[0146] As can be seen from Examples 1 to 14, amide compound-based additives significantly improved the cycle performance and storage performance of anode-free batteries. As can be seen from Examples 1 to 5, compared to 1-alkyl-3-methylimidazochloride salts, 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)amide salts, 1-alkyl-3-methylimidazole bis(fluorosulfonyl)amide salts, 1-butyl-3-methylimidazole bis(fluorosulfonyl)imide salts, and N-alkyl-N-methylpiperidine tetrafluoroborate were able to more effectively improve the cycle performance and storage performance of anode-free batteries. Here, 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)amide salts were most significant in improving the cycle performance and storage performance of anode-free batteries at room temperature and high temperature. As can be seen from Examples 9 to 11, potassium bis(oxalato)borate, a cation-shielding additive, was more effective in improving the cycle performance and storage performance of anode-free batteries. As can be seen from Examples 12 to 14, the use of fumed silica in the alloy additives was able to more effectively improve the cycle performance and storage performance of the battery.

[0147] As can be seen from Examples 15 to 19, the addition of two different additives effectively improved the cycle performance and storage performance of the battery. The co-addition of the ionic liquid additive 1-butyl-3-methylimidazole bis(fluorosulfonyl)imide salt and the amide compound additive 1,1,1-trifluorofluoro-N,N-dimethylmethanesulfonamide in Example 17 produced a synergistic effect, resulting in a three-fold increase in the number of cycles required for the negative electrode-free battery to reach 80% capacity at room temperature, a five-fold increase in the number of storage days, a ten-fold increase in the number of cycles at high temperature, and an 18-fold increase in the storage days compared to the additive-free negative electrode-free battery in Comparative Example 1.

[0148] As can be seen from Examples 20 to 27, the additives of the present application can be applied to various fluoroether solvents, and can effectively improve the cycle performance and storage performance of the battery in all electrolyte systems that use various fluoroether solvents as the main solvent, and can improve the electrochemical stability and cycle life of the battery.

[0149] As can be seen from Examples 28 to 30, the electrolyte solution according to the present invention was applied to various different sodium salts, and the batteries all showed excellent cycle performance and storage performance.

[0150] As can be seen from Examples 6, 31 to 34, when the mass content of the additive is 1-10% based on the total mass of the electrolyte, the batteries all exhibit a wider electrochemical window, and excellent cycle performance and storage performance at room and high temperatures.

[0151] As can be seen from Examples 6, 35 to 39, when the mass content of the fluoroether-based solvent was 20%-90% based on the total mass of the electrolyte, the batteries all exhibited a wider electrochemical window and excellent cycle and storage performance at room and high temperatures. As can be seen from Examples 6, 31 to 39, when the mass content of the electrolyte salt was 2%-70% based on the total mass of the electrolyte, the batteries all exhibited a wider electrochemical window and excellent cycle and storage performance at room and high temperatures. Furthermore, as can be seen from a comparison of Examples 6, 31 to 36 with Examples 37 to 39, when the mass content of the electrolyte salt was 20%-70%, the batteries' electrochemical window stability, cycle and storage performance were better.

[0152] As can be seen from the comparison between Examples 40 to 47 and Comparative Examples 18 to 23, the electrolyte solution according to the present application can be applied to various positive electrode materials, and of course, whether they are polyanions or layered oxides, they can effectively improve the width of the electrochemical stability window of the battery, the cycle performance of the battery, and the storage stability.

[0153] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiments without departing from the spirit of the present application, and other methods configured by combining some of the components of the embodiments, are also included within the scope of the present application. [Explanation of symbols]

[0154] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 cover plate.

Claims

1. 1. An electrolyte solution for a secondary battery, comprising a fluoroether-based solvent and an additive, wherein the additive comprises one or more of an ionic liquid-based additive, an amide compound-based additive, a cation-shielding additive, and an alloy-based additive.

2. 2. The electrolyte solution according to claim 1, wherein the cation of the ionic liquid additive comprises one or more of a nitrogen-containing onium ion and a phosphorus-containing onium ion, and the anion of the ionic liquid additive comprises one or more of a halogen ion, a phosphate ion, a borate ion, a sulfonylimide compound anion, and a sulfonamide compound anion.

3. The electrolyte solution according to claim 1 or 2, wherein the cation of the ionic liquid additive comprises one or more of 1-butyl-3-methylimidazolium, 1-benzyl-3-methylimidazolium, 3-methyl-1-ethoxycarbonylmethylimidazolium, 1-alkyl-3-methylimidazolium, 1-[(trimethylsilyl)methyl]benzotriazolium, N-alkyl-N-methylpiperidinium, 5-azoniaspiro[4.4]nonane, trihexyl(tetradecyl)phosphine ion, tetrabutylphosphine ion, and n-butyl-N-methylpyrrolidinium, and optionally 1-benzyl-3-methylimidazolium or 1-alkyl-3-methylimidazolium.

4. 4. The electrolytic solution according to claim 1, wherein the anion of the ionic liquid additive comprises one or more of a chloride ion, a bromide ion, an iodide ion, hexafluorophosphate, tetrafluoroborate, a dicyandiamide anion, a bis(fluorosulfonyl)amide anion, a bis(trifluoromethylsulfonyl)amide anion, a bis(fluorosulfonyl)imide anion, and a bis(trifluoromethylsulfonyl)imide anion, and optionally comprises one or more of a chloride ion, a bis(fluorosulfonyl)amide anion, a bis(trifluoromethylsulfonyl)amide anion, a bis(fluorosulfonyl)imide anion, and a bis(trifluoromethylsulfonyl)imide anion.

5. 4. The electrolytic solution according to claim 1, wherein the ionic liquid additive comprises one or more selected from the group consisting of 1-butyl-3-methylimidazole-bis(fluorosulfonyl)imide salts, 1-butyl-3-methylimidazole-bis(trifluoromethylsulfonyl)amide salts, 1-benzyl-3-methylimidazole-bis(fluorosulfonyl)imide salts, 1-benzyl-3-methylimidazole-bis(trifluoromethylsulfonyl)amide salts, 1-alkyl-3-methylimidazole-bis(fluorosulfonyl)imide salts, 1-alkyl-3-methylimidazole-bis(trifluoromethylsulfonyl)amide salts, 1-alkyl-3-methylimidazole-chlorine salts, and N-alkyl-N-methylpiperidine-tetrafluoroborate.

6. The amide compound additive comprises one or more of the compounds shown in Formula I, Formula II, or Formula III, Here, R 1 From R 9 are each independently hydrogen, a silyl group, a ketocarbonyl group, an unsubstituted or at least one fluorine atom-substituted C 1 -C 3 6. The electrolyte solution according to claim 1, wherein the alkyl group is selected from the group consisting of alkyl groups, unsubstituted and aromatic groups substituted with at least one fluorine atom.

7. The electrolyte solution according to any one of claims 1 to 6, wherein the amide compound-based additive includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylacetoacetamide, 1,1,1-trifluorofluoro-N,N-dimethylmethanesulfonamide, N,O-bis(trimethylsilyl)trifluoroacetamide, 2,3,6-trifluorobenzenesulfonamide, N,N-dimethyl-4-fluorobenzenesulfonamide, and N-methyl-N-trimethylsilane trifluoroacetamide.

8. 8. The electrolyte solution according to claim 1, wherein the cation-shielding additive comprises a salt whose cation is an alkali metal element or an alkaline earth metal element.

9. 9. The electrolyte solution of claim 1, wherein the cation shielding additive comprises one or more of lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, potassium hexafluorophosphate, potassium bis(oxalato)borate, potassium difluoro(oxalato)borate, potassium bis(fluorosulfonyl)imide, potassium bis(trifluoromethylsulfonyl)imide, cesium nitrate, cesium hexafluorophosphate, cesium bis(fluorosulfonyl)imide, cesium chloride, cesium bromide, calcium nitrate, strontium nitrate, and barium nitrate.

10. 10. The electrolyte solution according to claim 1, wherein the alloy additive is a compound containing a Group IVA or Group VA element.

11. 11. The electrolyte solution of claim 1, wherein the alloying additive comprises one or more of antimony trifluoride, antimony pentafluoride, tin difluoride, tin tetrafluoride, bismuth trichloride, and fumed silica.

12. 12. The electrolyte solution according to claim 1, wherein the mass content of the additive is 1-10% based on the total mass of the electrolyte solution.

13. The ether-based solvent is a fluoroether-based solvent, and the fluoroether-based solvent includes a compound represented by formula IV or a crown ether substituted with a fluorine atom, Here, R 7 , R 8 , R 9 are each independently hydrogen, unsubstituted or fluorine, straight-chain or branched C substituted with a hydroxyl group. 1 -C 6 alkyl groups, and R 7 , R 8 , R 9 At least one of R contains a fluorine atom, 7 and R 9 optionally, oxygen bonded thereto and R bonded thereto 8 The electrolyte solution according to any one of claims 1 to 12, characterized in that it forms a 5- or 6-membered saturated heterocyclic ring together with

14. The fluoroether solvents include 2,2,3,3-tetrafluoro-1,4-dimethoxybutane, 2-(2-ethoxyethoxy)-1,1,1-trifluoroethane, 1,2-bis(2,2-difluoroethoxy)ethane, 2-(2-(2,2-difluoroethoxy)ethoxy)-1,1,1-trifluoroethane, 1,2-bis(2,2,2-trifluoroethoxy)ethane, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 2,2,2-trifluoroethyl-1,1,2,3,3 ,3-hexafluoropropyl ether, 2,2-bis(trifluoromethyl)-1,3-dioxolane, 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxopentane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxopentane, octafluorotetrahydrofuran, ethylene glycol dimethyl ether substituted with at least one fluorine atom, diethylene glycol dimethyl ether substituted with at least one fluorine atom, 14. The electrolytic solution according to claim 1, wherein the electrolyte solution contains one or more of triethylene glycol dimethyl ether substituted with at least one fluorine atom, tetraethylene glycol dimethyl ether substituted with at least one fluorine atom, diethylene glycol diethyl ether substituted with at least one fluorine atom, diisopropyl ether substituted with at least one fluorine atom, dibutyl ether substituted with at least one fluorine atom, diethylene glycol dibutyl ether substituted with at least one fluorine atom, 1,4-diethoxybutane substituted with at least one fluorine atom, 15-crown ether-5 substituted with at least one fluorine atom, 12-crown ether-4 substituted with at least one fluorine atom, and 18-crown ether-6 substituted with at least one fluorine atom, and optionally at least one of 2,2,3,3-tetrafluoro-1,4-dimethoxybutane and 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxopentane.

15. 15. The electrolytic solution according to claim 1, wherein the mass content of the fluoroether-based solvent is 20% to 90% based on the total mass of the electrolytic solution.

16. 16. The electrolytic solution of claim 1, wherein the electrolyte salt is a sodium salt, and the sodium salt includes one or more of sodium nitrate, sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium tetrafluoroyttriate, sodium hexafluoroarsenate, sodium acetate, sodium trifluoroacetate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, and sodium (n-perfluorobutylsulfonyl)imide.

17. 17. The electrolyte solution according to claim 1, wherein the mass content of the electrolyte salt is 2%-70%, and optionally 20%-70%, based on the total mass of the electrolyte solution.

18. A secondary battery, comprising the electrolyte solution according to any one of claims 1 to 17.

19. 20. The secondary battery of claim 18, wherein the secondary battery comprises one or more of a lithium metal battery and a sodium metal battery.

20. 20. The secondary battery according to claim 18, wherein the secondary battery is a negative electrode-free sodium metal battery.

21. 21. The secondary battery according to claim 18, wherein the secondary battery includes a positive electrode plate, the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes one or more of a Prussian blue-based compound, a polyanion-type compound, and a layered oxide.

22. 22. The secondary battery according to claim 18, wherein a surface of the positive electrode active material particle has a coating layer, and the coating layer contains one or more of a carbon material, polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), aluminum oxide, zinc oxide, titanium oxide, zirconium oxide, magnesium oxide, silicon oxide, lanthanum oxide, sodium fluoride, lithium fluoride, and aluminum fluoride.

23. 23. The secondary battery according to claim 18, wherein the coating layer has a thickness of 2 nm to 1000 nm.

24. 24. The secondary battery according to claim 18, wherein the secondary battery includes a negative electrode plate, the negative electrode plate including a negative electrode current collector and an undercoating disposed on at least one surface of the negative electrode current collector, the undercoating including one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.

25. 25. The secondary battery according to claim 18, wherein the negative electrode current collector includes at least one of a metal foil, a metal foam current collector, a metal mesh current collector, a carbon felt current collector, a carbon cloth current collector, a carbon paper current collector, and a composite current collector.

26. The areal density of the undercoating is 2 g / m 2 -50 g / m 2 26. The secondary battery according to claim 24, wherein

27. 26. The secondary battery according to claim 24, wherein the undercoating has a thickness of 1 μm to 100 μm.

28. A battery module comprising the secondary battery according to any one of claims 18 to 27.

29. A battery pack comprising the secondary battery according to any one of claims 18 to 27 or the battery module according to claim 28.

30. 30. A power consumption device comprising at least one of the secondary battery according to any one of claims 18 to 27, the battery module according to claim 28, and the battery pack according to claim 29.

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