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

Abstract

The present application provides an electrolyte for a secondary battery, a secondary battery, a battery module, a battery pack, and a power consumption device. The electrolyte for a secondary battery includes an ester-based solvent and an additive, and the additive includes one or more of an ionic liquid-based additive, an amide compound-based additive, an inert cation 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 inert cation additive, and the alloy-based additive to an electrolyte containing an ester-based solvent, thereby significantly improving the interfacial stability of the secondary battery, improving the cycle performance and storage stability of the secondary battery, reducing gas production, 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, battery packs, and power consuming devices. [Background technology]

[0002] In recent years, secondary batteries have been widely used 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 also being put forward for their energy density, cycle performance, etc.

[0003] Electrolytes are the ion transport carriers in batteries, conducting ions between the positive and negative electrodes. As a key component of batteries, electrolytes are a key factor affecting battery cycle performance, rate performance, and safety. However, conventional electrolytes can cause side reactions with metal anodes and are incompatible with positive electrode materials, resulting in unstable chemical and electrochemical properties. Therefore, it is necessary to optimize the electrolyte to improve overall battery performance. 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 a secondary battery, which provides an electrolyte having stable chemical and electrochemical properties by adding one or more of an ionic liquid-based additive, an amide compound-based additive, an inert cation additive, and an alloy-based additive to an ester-based solvent, and a secondary battery manufactured using this electrolyte has improved interface stability, cycle performance, and storage stability.

[0005] A first aspect of the present application provides an electrolyte for a secondary battery, which includes an ester-based solvent and an additive, and the additive includes one or more of an ionic liquid-based additive, an amide compound-based additive, an inert cation additive, and an alloy-based additive.

[0006] In any embodiment, 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 halide ion, a phosphate ion, a borate ion, and a sulfonylimide-based anion.

[0007] By adding one or more additives selected from the group consisting of ionic liquid additives, amide compound additives, inert cation additives, and alloy additives to an electrolyte solution containing an ester solvent, the chemical and electrochemical stability of the electrolyte solution can be significantly improved, the cycle performance and storage stability of the secondary battery can be improved, and the amount of gas produced can be reduced, thereby increasing the overall safety of the secondary battery.

[0008] In any embodiment, the cation of the ionic liquid based additive may comprise 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 tetrabutylphosphine ion or n-butyl-N-methylpyrrolidinium.

[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)imide, and bis(trifluoromethanesulfonyl)imide, and is optionally hexafluorophosphate or bis(fluorosulfonyl)imide.

[0010] In any embodiment, the ionic liquid based additive may comprise one or more of tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imide salt, n-butyl-N-methylpyrrolidine hexafluorophosphate, n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imide salt, 1-butyl-3-methylimidazole bis(fluorosulfonyl)imide salt, 1-benzyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, 1-butyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, 1-benzyl-3-methylimidazole bis(fluorosulfonyl)imide salt, and optionally tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imide salt, n-butyl-N-methylpyrrolidine hexafluorophosphate, or n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imide salt.

[0011] The addition of an ionic liquid additive to an ester-based solvent electrolyte reinforces the solid electrolyte interface (SEI) film formed at the negative electrode, reducing direct reactions between the negative electrode and ester-based solvent molecules or free radicals. At the same time, the ionic liquid additive also repels solvent molecules at the electric double layer at the negative electrode / electrolyte interface, further reducing direct reactions between the negative electrode and ester-based solvent molecules or free radicals. This in turn enhances the stability at the negative electrode / electrolyte interface, further improving the cycle performance and storage stability of the battery at both room and high temperatures.

[0012] In any embodiment, the amide compound additive comprises one or more of the compounds shown in Formula I, Formula II, or Formula III: [ka] Here, 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 aryl group that is unsubstituted or substituted with at least one fluorine atom.

[0013] In any embodiment, the amide compound 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.

[0014] When an amide compound-based additive is added to an ester-based solvent electrolyte, the chemical and electrochemical stability of the battery can be increased, and the cycle performance and storage stability of the secondary battery can be significantly improved.

[0015] In either embodiment, the inert cationic additive comprises a salt whose cation is an alkali metal element or an alkaline earth metal element.

[0016] In any embodiment, the inert cation 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(trifluoromethanesulfonyl)imide, potassium hexafluorophosphate, potassium bis(oxalato)borate, potassium difluoro(oxalato)borate, potassium bis(fluorosulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, cesium nitrate, cesium hexafluorophosphate, cesium bis(fluorosulfonyl)imide, cesium chloride, cesium bromide, calcium nitrate, strontium nitrate, and barium nitrate.

[0017] By adding an inert cationic additive to an ester-based solvent electrolyte, the stability of the negative electrode interface of the battery can be improved, and the cycle performance and storage stability of the secondary battery can be improved.

[0018] In either embodiment, the alloying additive is a compound having a Group IVA or Group VA element.

[0019] In any embodiment, the alloying additives include one or more of antimony trifluoride, antimony pentafluoride, tin difluoride, tin tetrafluoride, bismuth trichloride, and vapor phase silicon dioxide.

[0020] Adding the alloy additive to an ester-based electrolyte can improve the stability of the SEI film and suppress the formation of dendrites on the negative electrode, thereby improving the cycle performance and storage stability of the secondary battery and reducing gas production, thereby contributing to improving the overall safety of the secondary battery.

[0021] In any embodiment, the mass content of the additive is 1% to 10% based on the total mass of the electrolyte solution.

[0022] When the mass content of the additive is 1 to 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 transport of ions in the battery, thereby improving the overall performance of the battery.

[0023] In any embodiment, the ester solvent comprises one or more of the compounds shown in Formula IV and Formula V: [ka] where R 10 is hydrogen, an olefinic group, a substituted or unsubstituted C 1-6 Alkyl groups, substituted or unsubstituted C 1-6 alkoxy groups, R 11 , R 12 , R 13 are each independently hydrogen, an olefinic group, or a substituted or unsubstituted C 1-6 alkyl groups, and R10 and R 11 optionally form a 4-, 5- or 6-membered ring together with the carbon or oxygen to which they are attached, and this ring optionally has a double bond, and the hydrogen in this ring optionally is replaced by a halogen, C 1-3 substituted with alkyl groups, R 12 and R 13 optionally form a 4-, 5- or 6-membered ring together with the sulfur or oxygen to which they are attached.

[0024] In any embodiment, the ester-based solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, γ-butyrolactone, 1,3-propane sultone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate, and ethyl butyrate.

[0025] In any embodiment, the mass content of the ester solvent is 20% to 90%, and optionally 40% to 70%, based on the total mass of the electrolyte solution.

[0026] When the mass content of the ester-based solvent is 20% to 90% 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, thereby improving the chemical and electrochemical stability of the battery.

[0027] In any embodiment, the electrolyte includes a sodium salt, which may include 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(trifluoromethanesulfonyl)imide, and sodium (n-perfluorobutylsulfonyl)imide.

[0028] In any embodiment, the mass content of the sodium salt is 2% to 70%, and optionally 30% to 60%, based on the total mass of the electrolyte.

[0029] When the mass content of the electrolyte salt is 2% to 70% based on the total mass of the electrolyte, a stable SEI film is formed at the interface between the negative electrode and the electrolyte, improving the chemical and electrochemical stability of the battery and enhancing the cycle performance, storage stability and safety of the battery.

[0030] A second aspect of the present application provides a secondary battery, which includes the electrolyte solution of the first aspect.

[0031] In either embodiment, the secondary battery is a sodium metal battery.

[0032] In either embodiment, the secondary battery is a non-anode sodium metal battery.

[0033] 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.

[0034] In any embodiment, the surfaces of the particles of the positive electrode active material have a coating layer, and the coating layer includes one or more of a carbon material (amorphous, 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.

[0035] The coating layer on the surface of the positive electrode active material particles can prevent side reactions caused by direct contact between the surface of the positive electrode metal and the electrolyte, suppress the elution of the positive electrode transition metal, and improve the stability of the electrode / electrolyte interface.

[0036] In any embodiment, the coating layer has a thickness of 2 nm to 1000 nm.

[0037] A coating layer with an appropriate thickness can effectively improve the performance, and can avoid the problem of the coating layer being too thick, which causes the positive electrode film resistance to be too high and reduces the battery performance.

[0038] 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.

[0039] In any embodiment, the negative electrode current collector includes at least one of a metal foil material, 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.

[0040] In any embodiment, the areal density of the undercoating is less than 2 g / m 2 ~50 g / m 2 is.

[0041] In either embodiment, the undercoating has a thickness of 1 μm to 100 μm.

[0042] A suitable undercoating can effectively guide the anode deposition, reduce the occurrence of anode sodium dendrites, and improve the uniformity of sodium metal deposition. An undercoating with the appropriate surface density and thickness can effectively function as a non-anode, improving the energy density and safety performance of the battery.

[0043] A third aspect of the present application provides a battery module, which includes the secondary battery of the second aspect.

[0044] 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.

[0045] A fifth aspect of the present application provides a power consuming device, which includes 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]

[0046] [Figure 1] 1 is a schematic diagram of a secondary battery according to one embodiment of the present application. [Figure 2] FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. [Figure 3] 1 is a schematic diagram of a battery module according to one embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to one embodiment of the present application; [Figure 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to one embodiment of the present application. [Figure 6] 1 is a schematic diagram of a power consumption device powered by a secondary battery according to one embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0047] 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.

[0048] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and 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 any combination is possible; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also possible. 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 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all possible. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand notation for any combination of real numbers 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.

[0049] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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).

[0054] Ester-based solvents are commonly used as electrolytes in secondary batteries. However, electrolytes containing ester-based solvents are susceptible to reduction due to a narrow electrochemical stability window on the reduction side. Due to this susceptibility to reduction, the solid electrolyte interface (SEI) formed is unstable, resulting in constant electrolyte consumption during cycling and severely shortening the cycle life. Furthermore, direct side reactions occur between electrolytes containing ester-based solvents and metal electrodes, and solvation complexes formed by the dissolution of electrolyte salts exacerbate these side reactions. The decomposition pathway between electrolytes containing ester-based solvents and sodium typically involves CO cleavage, and the by-products are often flammable gases such as carbon monoxide, which significantly compromises the safety of metal batteries.

[0055] [Electrolyte for secondary batteries] Based on this, the present application provides an electrolyte solution for a secondary battery, which includes an ester-based solvent and an additive, and the additive includes one or more of an ionic liquid-based additive, an amide compound-based additive, an inert cation additive, and an alloy-based additive.

[0056] As used herein, "ester solvent" refers to an organic solvent containing an ester group. As can be appreciated, the ester solvent may include any substituent, such as a halogen.

[0057] 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 distinction between additives, main solvents, and electrolyte salts lies solely in their respective amounts in the electrolyte solution, and solvents or salts present in relatively small amounts may be collectively referred to as additives.

[0058] As used herein, the term "ionic liquid additive" refers to a salt that is added to an electrolyte in a relatively small amount, is composed entirely of cations and anions, and exists in a liquid state at or near room temperature, where room temperature refers to 25°C ± 5°C.

[0059] In this specification, the term "amide compound-based additive" refers to an additive that is added to an electrolyte in a relatively small amount, [ka] It refers to a compound having the formula:

[0060] As used herein, the term "inert cation additive" refers to a salt that is added to the electrolyte in a relatively small amount and is capable of ionizing cations. The cations adsorb only to the electrode surface and do not participate in the electrode redox reaction, and can also function to eliminate shuttle ions and free radicals that cause side reactions at the bilayer interface of the negative electrode.

[0061] As used herein, the term "alloying additive" refers to a compound that is added to the electrolyte solution in a relatively small amount and has an element that can form an alloy in the SEI film with a metal cation in the electrolyte salt.

[0062] 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 an inert cation 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 an inert cation 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, an inert cation additive, and an alloy-based additive to an electrolyte containing an ester-based solvent, the occurrence of side reactions between the metal anode and the electrolyte and the resulting unstable solid electrolyte interface (SEI) film can be suppressed, thereby significantly improving the chemical and electrochemical stability of the electrolyte, improving the cycle performance and storage stability of the secondary battery, and enhancing the safety of the secondary battery.

[0063] 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 halide ion, a phosphate ion, a borate ion, and a sulfonylimide-based anion. In some embodiments, the cation of the ionic liquid additive comprises 1-butyl-3-methylimidazolium ([Bmin] + ), 1-benzyl-3-methylimidazolium ([Bzmin] + ), 3-methyl-1-ethoxycarbonylmethylimidazolium ([Etmim] + ), 1-alkyl-3-methylimidazolium ([Cnmim] + ), 1-[(trimethylsilyl)methyl]benzotriazolium ([SiMBIM] + ), N-Alkyl-N-methylpiperidinium ([CnC1pip] + ), 5-azoniaspiro[4.4]nonane ([AS[mn]]+ ), trihexyl(tetradecyl)phosphine ion ([TfN] + ), tetrabutylphosphine ion ([Pnnnn] + ), n-butyl-N-methylpyrrolidinium ([Pyr 14 ] + ), optionally tetrabutylphosphine ion or n-butyl-N-methylpyrrolidinium.

[0064] In some embodiments, the anion of the ionic liquid based additive is a chloride ion ([Cl] - ), bromide ion ([Br] - ), iodine ion ([I] - ), hexafluorophosphate ion ([PF6] - ), tetrafluoroborate ion ([BF4] - ), dicyandiamide anion ([N(CN)2] - ), bis(fluorosulfonyl)imide anion ([FSI] - ), bis(trifluoromethanesulfonyl)imide ([TFSI] - ), optionally a hexafluorophosphate ion or a bis(fluorosulfonyl)imide anion.

[0065] In some embodiments, the ionic liquid based additive comprises one or more of tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imide salt, n-butyl-N-methylpyrrolidine hexafluorophosphate, n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imide salt, 1-butyl-3-methylimidazole bis(fluorosulfonyl)imide salt, 1-benzyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, 1-butyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, 1-benzyl-3-methylimidazole bis(fluorosulfonyl)imide salt, and optionally tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imide salt, n-butyl-N-methylpyrrolidine hexafluorophosphate, n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imide salt.

[0066] The addition of ionic liquid additives to ester-based solvents, particularly ionic liquids containing bis(fluorosulfonyl)imide or bis(trifluoromethanesulfonyl)imide, can reinforce the SEI film formed on the anode and reduce direct reactions between the anode and ester-based solvent molecules or free radicals. At the same time, the ionic liquid additives can also repel solvent molecules at the electric double layer at the anode-electrolyte interface, further reducing direct reactions between the anode and ester-based solvent molecules or free radicals. These actions enhance the stability at the anode-electrolyte interface, further improving the cycle performance and storage stability of the battery at both room and high temperatures.

[0067] In some embodiments, the amide compound additive comprises one or more of the compounds shown in Formula I, Formula II, or Formula III: [ka] Here, 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 aryl group that is unsubstituted or substituted with at least one fluorine atom.

[0068] As used herein, the term "silane group" refers to a group consisting of -Si(R 14 )(R 15 )(R 16 ) group, where R 14 , R 15 , R 16 are each independently hydrogen, substituted or unsubstituted C 1-3 The silane groups are selected from alkyl groups. Exemplary silane groups include, but are not limited to, -SiH3, -Si(CH3)3.

[0069] As used herein, the term "ketocarbonyl group" refers to the group --R--CO--R'--, where R and R' are both hydrocarbon groups.

[0070] As used herein, the term "aryl" 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.

[0071] As used herein, the term "C1-C3 alkyl group" refers to a straight or branched hydrocarbon chain group consisting solely of carbon and hydrogen atoms, with no unsaturation in the group, having from one to three carbon atoms, and attached to the rest of the molecule by a single bond.

[0072] As used herein, the term "substituted" means that at least one hydrogen atom of the compound or chemical moiety is replaced with a substituent of 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.

[0073] In some embodiments, the amide compound additive comprises a sulfonyl amide compound shown in Formula III:

[0074] In some embodiments, the amide compound additive comprises one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N,N-dimethylacetoacetamide (DMAA), 1,1,1-trifluorofluoro-N,N-dimethylmethanesulfonamide (DMCF3SA), N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), 2,3,6-trifluorobenzenesulfonamide (TFBFSA), N,N-dimethyl-4-fluorobenzenesulfonamide (DMFBFSA), and N-methyl-N-trimethylsilane trifluoroacetamide (MSTFA).

[0075] When an amide compound-based additive is added to an ester-based solvent, the SEI film formed on the negative electrode contains inorganic nitrides. The presence of inorganic nitrides improves the film's stability and oxygen resistance, thereby significantly enhancing the chemical and 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 ester-based solvent, thereby preventing the Lewis acidic components in the electrolyte from continuing to react with the negative electrode and further improving the negative electrode interfacial stability of the battery. Due to these effects, amide compound-based additives can significantly improve the cycle performance and storage stability of secondary batteries, especially metal batteries (including batteries without a negative electrode).

[0076] In some embodiments, the inert cationic additive comprises a salt in which the cation is an alkali metal element or an alkaline earth metal element.

[0077] As used herein, alkali metal elements refer to metal elements in Group IA of the periodic table of the elements, excluding hydrogen (H). In some embodiments, the inert cation additive includes lithium, potassium, or cesium.

[0078] As used herein, alkaline earth metal elements refer to Group IIA elements in the periodic table of the elements. In some embodiments, the inert cationic additive comprises calcium, strontium, or barium.

[0079] In some embodiments, the inert cation additive is lithium nitrate (LiNO), lithium perchlorate (LiClO), lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), potassium hexafluorophosphate (KPF), potassium bis(oxalato)borate (KBOB), potassium difluoro(oxalato)borate (KDFOB), potassium bis(fluorosulfonyl)imide (KFSI), potassium bis(trifluoromethanesulfonyl)imide (KTFSI), cesium nitrate (CsNO3), cesium hexafluorophosphate (CsPF6), cesium bis(fluorosulfonyl)imide (CsFSI), cesium chloride (CsCl), cesium bromide (CsBr), calcium nitrate (Ca(NO3)2), strontium nitrate (Sr(NO3)2), and barium nitrate (Ba(NO3)2).

[0080] The addition of an inert cation additive to an ester-based solvent can introduce cations different from the metal ions in the electrolyte salt. The cations in the inert cation additive can not only eliminate shuttle ions and free radicals that cause side reactions in the electric double layer at the negative electrode interface, but also guide the metal ions in the electrolyte salt to uniformly deposit and exfoliate at the negative electrode. At the same time, some anions contained in the inert cation additive can increase the inorganic component in the SEI film and stabilize the SEI, thereby further improving the stability of the negative electrode interface and improving the cycle performance and storage stability of secondary batteries, especially metal batteries (including negative electrode-less batteries).

[0081] In some embodiments, the alloying additive is a compound having a Group IVA or Group VA element.

[0082] In some embodiments, the alloying additive comprises one or more of antimony trifluoride (SbF), antimony pentafluoride (SbF), tin difluoride (SnF), tin tetrafluoride (SnF), bismuth trichloride (BiCl), and silicon dioxide.

[0083] In some embodiments, the silicon dioxide is vapor phase silicon dioxide (F—SiO 2 ).

[0084] As used herein, the term "fumed silica," also known as fumed white carbon, is amorphous nano-silicon dioxide particles.

[0085] When the alloy additive is added to an ester-based electrolyte, a two-layer SEI film can be formed on the negative electrode. One layer of the SEI film contains a large amount of an alloy component consisting of a Group IVA or Group VA element and sodium, and the other layer of the SEI film contains a large amount of an inorganic material such as sodium fluoride. This can improve the stability of the SEI film and suppress the formation of dendrites in the negative electrode, thereby improving the cycle performance and storage stability of the secondary battery and reducing gas production, thereby contributing to improving the overall safety of the secondary battery.

[0086] In some embodiments, the mass content of the additive is 1 to 10% based on the total mass of the electrolyte.

[0087] 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.

[0088] When the mass content of the additive is 1 to 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 transport of ions in the battery, thereby improving the overall performance of the battery.

[0089] In some embodiments, the ester solvent comprises one or more of the compounds shown in Formula IV, the compounds shown in Formula V, [ka] where R 10 is hydrogen, an olefinic group, a substituted or unsubstituted C 1-6 Alkyl groups, substituted or unsubstituted C 1-6 alkoxy groups, R 11 , R 12 , R 13 are each independently hydrogen, an olefinic group, or a substituted or unsubstituted C 1-6 alkyl groups, and R 10 and R 11optionally form a ring structure together with the carbon and oxygen to which they are attached, and this ring optionally has a double bond, and the hydrogen in this ring optionally is replaced by a halogen, C 1-3 substituted with alkyl groups, R 12 and R 13 optionally form a ring structure together with the sulfur and oxygen to which they are attached.

[0090] As used herein, the term "C1-6 alkyl group" can be understood with reference to the definition of the term "C1-3 alkyl group."

[0091] As used herein, the term "olefinic group" refers to an unsaturated hydrocarbon group having at least one carbon-carbon double bond.

[0092] As used herein, the term "cyclic structure" refers to a structure in which atoms in a molecule are arranged in a ring. The number of rings in the cyclic structure is not limited, and may be, for example, a 4-membered ring, a 5-membered ring, a 6-membered ring, or a 7-membered ring. For example, Formula IV forming a cyclic structure includes, but is not limited to, γ-butyrolactone, and Formula V forming a cyclic structure includes, but is not limited to, 1,3-propane sultone (1,3-PS), 3-fluoro-1,3-propane sultone (FPS), 1-methyl-1,3-propane sultone (2,4-BS), 1,4-butane sultone (BS), 1,4-butene sultone (BST), and 1,3-propylene sultone (PES).

[0093] In some embodiments, the ester solvent comprises a sulfonate ester compound shown in Formula V:

[0094] In some embodiments, the ester-based solvent comprises at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), γ-butyrolactone (BL), 1,3-propane sultone (1,3-PS), methyl propionate (MP), methyl butyrate (MB), ethyl acetate (EA), ethyl propionate (EP), propyl propionate (PP), and ethyl butyrate (EB).

[0095] In some embodiments, the mass content of the ester-based solvent is 20% to 90% based on the total mass of the electrolyte solution.

[0096] In some embodiments, the mass content of the ester-based solvent is 40% to 70% based on the total mass of the electrolyte solution.

[0097] In some embodiments, the mass content of the ester-based solvent is optionally 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.

[0098] When the mass content of the ester solvent is 20% to 90%, a stable SEI film is formed at the interface between the negative electrode and the electrolyte, which can improve the chemical and electrochemical stability of the battery.

[0099] In some embodiments, the electrolyte includes a sodium salt, and the sodium salt may be sodium nitrate (NaNO), sodium perchlorate (NaClO), sodium hexafluorophosphate (NaPF), sodium tetrafluoroborate (NaBF), sodium tetrafluoroyttrium salt (NaYF), sodium hexafluoroarsenate (NaAsF), sodium acetate (CHCOONa), sodium trifluoroacetate (CFCOONa), sodium bis(oxalato)borate (NaBOB), sodium difluoro(oxalato)borate (NaDFOB), sodium tetraphenylborate (NaB(C6H5)4), sodium trifluoromethanesulfonate (NaF(C6H5)4), sodium tetra ... M( NaOTF), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium (n-perfluorobutylsulfonyl)imide (NaFNFSI).

[0100] In some embodiments, the mass content of the sodium salt is 2% to 70%, and optionally 30% to 60%, based on the total mass of the electrolyte.

[0101] In some embodiments, the mass content of the sodium salt is optionally 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70% based on the total mass of the electrolyte.

[0102] When the mass content of the sodium salt is 2% to 70% based on the total mass of the electrolyte, the electrolyte of the present application can effectively improve the chemical and electrochemical stability, cycle performance, and storage stability of the battery.When the mass content of the sodium salt is 20% to 70% based on the total mass of the electrolyte, the high concentration of electrolyte salt can further reduce the free state solvent molecules in the solvent, reduce side reactions between the solvent and the negative electrode, and improve the cycle performance, storage stability, and safety of the battery.

[0103] [Secondary battery] In some embodiments, a secondary battery comprises the above electrolyte.

[0104] In some embodiments, the secondary battery is a sodium metal battery.

[0105] A sodium metal battery refers to a battery in which the negative electrode is sodium metal.

[0106] In some embodiments, the secondary battery is a negative electrode-less sodium metal battery. A negative electrode-less sodium metal battery does not use a negative electrode active material, but instead uses only a negative electrode current collector as the negative electrode. The negative electrode sodium plating is completed during the initial charging process, and then returns to the positive electrode during discharging, achieving a charge-discharge cycle. Because there is no negative electrode material and only a negative electrode current collector is used, a negative electrode-less battery effectively overcomes the deficiencies of sodium metal batteries and can achieve a higher energy density than a metallic sodium negative electrode.

[0107] In some embodiments, the CB value of the anodeless sodium metal battery is 0.1 or less. The CB value is the capacity per unit area of ​​the negative electrode plate in the secondary battery divided by the capacity per unit area of ​​the positive electrode plate. Because the anodeless sodium metal battery does not contain an active negative electrode material, the capacity per unit area of ​​the negative electrode plate is relatively small, and the CB value of the sodium secondary battery is 0.1 or less.

[0108] Because ester-based solvents have a relatively high highest occupied molecular orbital (HOMO), the electrochemical stability window of the electrolyte after dissolving the electrolyte salt therein has a higher potential toward the oxidation side. However, ester-based solvents still have chemical and electrochemical stability issues when combined with positive electrode active materials, especially layered oxides with high energy density and high operating potential. The present application proposes adding one or more of ionic liquid-based additives, amide compound-based additives, inert cation additives, and alloy-based additives to ester-based solvents to form a stable SEI film at the electrode / electrolyte interface, reducing direct side reactions between the electrode metal and ester-based solvent molecules or free radicals in the electrolyte, thereby significantly improving the cycle performance, storage stability, and safety of anodeless sodium batteries.

[0109] 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.

[0110] The layered oxide may optionally be a layered transition metal oxide, and 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。

[0111] Polyanionic compounds include metal ions, transition metal ions, and tetrahedral (YO4) n- The compound may have 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 state of

[0112] The Prussian blue compound may be a compound having 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。

[0113] 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.

[0114] Anodeless sodium metal batteries exhibit good cycle performance in ester-based electrolytes, particularly when combined with polyanion positive electrodes containing sodium vanadium phosphate (Na3V2(PO4)3) or sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7). Layered oxides have higher energy density, but suffer from poor compatibility with conventional electrolytes and poor cycle performance. Matching the layered oxide with the electrolyte of the present invention can effectively improve cycle life.

[0115] 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, polyaniline (PANI), polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT), aluminum oxide (Al2O3), zinc oxide (ZnO), titanium oxide (TiO2), zirconium oxide (ZrO2), magnesium oxide (MgO), silicon oxide (SiO2), lanthanum oxide (La2O3), sodium fluoride (NaF), lithium fluoride (LiF), and aluminum fluoride (AlF3), and the carbon material includes one or more of amorphous carbon, graphite, and graphene.

[0116] The coating layer can effectively improve the stability of the positive electrode active material, reduce metal leaching and particle crushing during the cycling process of the positive electrode active material, and effectively improve the cycling performance and storage stability of the battery.

[0117] In some embodiments, the coating layer has a thickness between 2 nm and 1000 nm.

[0118] In some embodiments, the thickness of the coating layer is optionally 2 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm.

[0119] A coating layer with an appropriate thickness can effectively improve the performance, and can avoid the problem of the coating layer being too thick, which causes the positive electrode film resistance to be too high and reduces the battery performance.

[0120] In some embodiments, 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.

[0121] In some embodiments, the areal density of the undercoating is 2 g / m 2 ~50 g / m 2 is.

[0122] In some embodiments, the undercoating has a thickness between 1 μm and 100 μm.

[0123] An undercoating within the above range can effectively guide the anode deposition, reduce the occurrence of anode sodium dendrites, and improve the uniformity of sodium metal deposition. Furthermore, an undercoating with an appropriate surface density and thickness can effectively function as a non-anode, improving the energy density and safety performance of the battery.

[0124] In some embodiments, the current collector of the anodeless sodium metal battery comprises at least one of a metal foil material, 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.

[0125] In some embodiments, the metal foil material 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, etc. 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, with a polymer base film positioned in the middle and metal foil material on both sides. The composite current collector may have a metal foil material on one side of the polymer base film. The polymer base film is optionally one of polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polychloroethylene, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyparaphenylene terephthalamide, polypropylethylene, polyformaldehyde, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, and polycarbonate. In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and electrolyte.

[0126] 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.

[0127] 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.

[0128] 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 a side plate connected to the bottom plate, where the bottom plate and the side plate 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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 and may 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.

[0134] 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.

[0135] The power consumption device can be selected from a secondary battery, a battery module, or a battery pack depending on its usage needs.

[0136] 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.

[0137] Other examples of the device may be a mobile phone, a tablet computer, a laptop computer, etc. These devices are generally required to be thin and can use a secondary battery as a power source.

[0138] Example The following describes examples of the present application. The examples described below are illustrative and are intended only to interpret the present application, and should not be understood as limitations on the present application. In the examples, specific techniques or conditions are not shown, and the techniques or conditions are carried out according to the techniques or conditions described in documents in the art or according to product specifications. The reagents or instruments used do not indicate their manufacturers, and are all ordinary products that are commercially available.

[0139] 1. Manufacturing method Example 1 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. The positive electrode slurry was then applied to the surface of an aluminum foil using an extrusion coater in accordance with 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 thickness of 2.5 g / cm. 3 The final positive electrode plate was obtained by cold pressing at the design pressure density.

[0140] 2. Manufacturing of negative electrode plates Carbon nanotubes and sodium carboxymethyl cellulose are added to water in a mass ratio of 1:2 and stirred to form a uniform slurry. The slurry is applied to a negative electrode current collector. After the slurry dries, an undercoating is formed. The negative electrode plate is then dried and cut to obtain a negative electrode plate with a no-anode structure. The areal density of the undercoating is 10 g / m. 2 It was.

[0141] 3. Separator A polyethylene film (PE separator) was used as the separator.

[0142] 4. Electrolyte production In an argon gas atmosphere glove box (H2O<0.1 ppm, O2<0.1 ppm), diethyl carbonate and ethyl methyl carbonate were mixed in a volume ratio of 1:1, and sodium hexafluorophosphate was dissolved in the above ester-based mixed solvent. Subsequently, n-butyl-N-methylpyrrolidine-hexafluorophosphate was added to the above prepared solution, so that the mass of sodium hexafluorophosphate accounted for 20% of the total mass of the electrolyte, and n-butyl-N-methylpyrrolidine-hexafluorophosphate accounted for 5% of the total mass of the electrolyte, thereby obtaining the electrolyte of Example 1.

[0143] 5. Battery manufacturing The positive electrode plate, separator, and negative electrode plate were folded in order, with the separator positioned between the positive electrode plate and the negative electrode plate to provide isolation, and the electrolyte was added to assemble into a button battery.

[0144] The specific parameters are as shown in Table 1.

[0145] In Examples 2 to 23, the components of the secondary battery electrolyte solution were adjusted, and the specific parameters are as shown in Table 1. Here, in Examples 10 to 13, the solvent in the electrolyte solution was diethyl carbonate and fluoroethylene carbonate, and the volume ratio of the two was 2:1. In Example 23, the mass content of sodium bis(trifluoromethanesulfonyl)imide in the electrolyte solution was 50%, and the mass content of sodium hexafluorophosphate in the electrolyte solution was 20%.

[0146] In Examples 24 to 27, 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.

[0147] In Examples 28-31, the positive electrode active material was Na coated with ZrO2, respectively. 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg1 / 18 O2 (the thickness of the ZrO2 coating layer is 30 nm), and the specific parameters of the other components are as shown in Table 1.

[0148] In Comparative Examples 1 to 10, the components of the electrolyte solution or the positive electrode active material of the secondary battery were adjusted, with specific parameters as shown in Table 1, and the manufacturing method was basically the same as in Example 1. Here, in Comparative Example 2, the volume ratio of diethyl carbonate to fluoroethylene carbonate was 2:1. In Comparative Example 8, the mass content of sodium bis(trifluoromethanesulfonyl)imide in the electrolyte solution was 50%, and the mass content of sodium hexafluorophosphate in the electrolyte solution was 20%.

[0149] 2. Battery performance test 1) Electrochemical stable window test An electrochemical workstation was used to perform the electrolyte window test. The test voltage range was 1.0 to 5.0 V, and the scan rate was 0.1 mV / s. The electrochemical stability window of the electrolyte was confirmed based on the onset of the peak potential in the CV curve. All cyclic voltammetry (CV) tests in this experiment were completed on a Solartron 1470 multichannel electrochemical workstation in the UK.

[0150] 2) Room temperature / high temperature cycle performance At 25 / 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), 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 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 when the discharge capacity was 80% was recorded.

[0151] 3) Room temperature / high temperature storage performance After allowing the fabricated full cells to stand for 30 minutes at 25°C / 60°C, they were charged to 4 V (layered oxide cathode) or 3.7 V (sodium iron pyrophosphate cathode) at a constant current of 0.1 C rate, then charged to a constant voltage of 4 V at 0.01 C, allowed to stand for 5 minutes, and the thickness of the full cells was measured. After storing at 25°C / 60°C for 60 days, the thickness of the full cells was measured and the thickness expansion rate of the battery was calculated using the following formula: full cell thickness expansion rate = [(thickness after storage - thickness before storage) / thickness before storage] × 100%. The test process for the comparative example and other examples was the same as above.

[0152] 3. Analysis of Test Results for Each Example and Comparative Example The batteries of the examples and comparative examples were manufactured by the above method, and the performance parameters of each item were measured. The results are shown in Tables 1 and 2 below.

[0153] Table 1 [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4] [Table 1-5] [Table 1-6] [Table 1-7]

[0154] Table 2 [Table 2-1] [Table 2-2] [Table 2-3]

[0155] As is clear from Tables 1 and 2, the electrolytes of the anode-less sodium batteries of Examples 1 to 31 contained an ester-based solvent and an additive, where the ester-based solvent was the main solvent of the electrolyte, and the additive was one or more selected from the group consisting of an ionic liquid-based additive, an amide compound-based additive, an inert cation additive, and an alloy-based additive.

[0156] Examples 1 to 9 all showed better cycle performance and lower gas production than Comparative Example 1, and Examples 10 to 13 all showed better cycle performance and lower gas production than Comparative Example 2. Here, the addition of an ionic liquid-based additive and an amide compound-based additive further widened the electrochemical stability window, providing the electrolyte with better electrochemical stability.

[0157] As can be seen from the comparison between Examples 14-15 and Comparative Examples 3-4, the electrolyte of the present application can be applied to different types of sodium salts, and all of them can effectively improve the cycle performance of the battery and reduce the gas production of the battery.

[0158] As can be seen from the comparison between Examples 1, 16 to 19 and Comparative Example 1, when the mass content of the additive was 1% to 10%, the cycle performance of the battery could be effectively improved and the gas production of the battery could be reduced.

[0159] As can be seen from the comparison between Examples 20 to 23 and Comparative Examples 5 to 8, the electrolyte of the present application can be applied to electrolyte systems of different concentrations, and in all of the electrolyte systems of different concentrations, it was possible to improve the battery cycle performance, reduce gas production, and widen the electrochemical stability window. In particular, in high-concentration electrolyte systems, the electrolyte of the present application was able to further improve battery performance on the basis of high cycle performance by improving the solvation structure of sodium ions.

[0160] As can be seen from Examples 1 to 9, the ionic liquid additives significantly improved the cycle performance and storage stability of the anodeless battery. As can be seen from Examples 1 to 4, n-butyl-N-methylpyrrolidine hexafluorophosphate and tetrabutylphosphine bis(fluorosulfonyl)imide salt were able to more effectively improve the cycle performance and storage stability of the anodeless battery. Here, n-butyl-N-methylpyrrolidine hexafluorophosphate significantly improved the cycle performance and storage stability of the anodeless battery at room temperature and high temperature. As can be seen from Examples 9 to 11, the inert cation additives lithium bis(oxalato)borate and potassium bis(oxalato)borate significantly improved the cycle performance and storage stability of the anodeless battery.

[0161] As can be seen from the comparison between Examples 24 to 31 and Comparative Examples 9 and 10, the electrolyte solution of the present invention can be applied to various cathode materials, and can effectively improve the electrochemical stability window width, cycle performance, and storage stability of the battery, regardless of whether the material is a polyanion or a layered oxide. In particular, the electrochemical cycle stability at high voltages of layered oxides can be effectively improved.

[0162] 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 and other methods that are constructed by combining some of the components of the embodiments are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application. [Explanation of symbols]

[0163] 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. An electrolyte solution for a secondary battery, comprising an ester-based solvent and an additive, wherein the additive comprises one or more of an ionic liquid-based additive, an amide compound-based additive, an inert cation additive, and an alloy-based additive.

2. 2. The electrolyte solution of claim 1, wherein the cations of the ionic liquid-based additive include one or more of a nitrogen-containing onium ion and a phosphorus-containing onium ion, and the anions of the ionic liquid-based additive include one or more of a halogen ion, a phosphate ion, a borate ion, and a sulfonylimide-based 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 is tetrabutylphosphine ion or n-butyl-N-methylpyrrolidinium.

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

5. 5. The electrolytic solution according to claim 1, wherein the ionic liquid-based additive comprises one or more of tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imide salt, n-butyl-N-methylpyrrolidine hexafluorophosphate, n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imide salt, 1-butyl-3-methylimidazole bis(fluorosulfonyl)imide salt, 1-benzyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, 1-butyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, and 1-benzyl-3-methylimidazole bis(fluorosulfonyl)imide salt, and optionally tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imide salt, n-butyl-N-methylpyrrolidine hexafluorophosphate, or n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imide salt.

6. The amide compound additive comprises one or more of the compounds shown in Formula I, Formula II, or Formula III, 【Chemical 1】 Here, R １ From R ９ are each independently hydrogen, a silyl group, a ketocarbonyl group, or an unsubstituted or at least one fluorine-substituted C １ -C ３ 6. The electrolyte solution according to claim 1, wherein the alkyl group is selected from the group consisting of an alkyl group and an aryl group that is unsubstituted or 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 inert cationic 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 inert cation-based 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(trifluoromethanesulfonyl)imide, potassium hexafluorophosphate, potassium bis(oxalato)borate, potassium difluoro(oxalato)borate, potassium bis(fluorosulfonyl)imide, potassium bis(trifluoromethanesulfonyl)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 silicon dioxide, and optionally, the silicon dioxide is gas-phase silicon dioxide.

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

13. The ester solvent comprises one or more of the compounds represented by formula IV and formula V: 【Chemistry 2】 Here, R １０ is hydrogen, an olefin group, a substituted or unsubstituted C １－６ alkyl group, substituted or unsubstituted C １－６ alkoxy groups, R １１ , R １２ , R １３ are each independently hydrogen, an olefin group, a substituted or unsubstituted C １－６ alkyl groups, R １０ and R １１ optionally form a cyclic structure together with the carbon and oxygen to which they are bonded, and the cyclic structure optionally has a double bond, and the hydrogen in the cyclic structure optionally is replaced by a halogen, C １－３ substituted with an alkyl group, R １２ and R １３ The electrolyte solution according to any one of claims 1 to 12, characterized in that: selectively form a cyclic structure together with the sulfur and oxygen to which they are bonded.

14. The electrolytic solution according to any one of claims 1 to 13, characterized in that the ester-based solvent contains at least one of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, γ-butyrolactone, 1,3-propane sultone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate, and ethyl butyrate.

15. The electrolyte solution according to any one of claims 1 to 14, wherein the mass content of the ester-based solvent is 20% to 90%, and optionally 40% to 70%, based on the total mass of the electrolyte solution.

16. 16. The electrolytic solution of claim 1, wherein the sodium salt comprises 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(trifluoromethanesulfonyl)imide, and sodium (n-perfluorobutylsulfonyl)imide.

17. 17. The electrolyte according to claim 16, wherein the mass content of the sodium salt is 2% to 70%, and optionally 30% to 60%, based on the total mass of the electrolyte.

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

19. 20. The secondary battery according to claim 18, wherein the secondary battery is a sodium metal battery.

20. 20. The secondary battery according to claim 18, wherein the secondary battery is a non-anode 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 21, wherein a surface of a particle of the positive electrode active material 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 22, 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 of claim 24, wherein the negative electrode current collector 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.

26. The areal density of the undercoating is 2 g / m ２ Up to 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 consuming 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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